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GIS Glossary

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bat file

A file that contains commands that can be run in a command window. It is used to perform repetitive tasks and to run scheduled commands, and is also referred to as a batch file.

dbf

A database file format. In the ArcWeb Services Web site, users can upload data into Builder as either a DBF file or a shapefile (SHP).

NET

A framework, developed by Microsoft, that compiles any of several COM-based programming languages into machine-executable language. The .NET framework also acts as a Web service toolkit.

1NF

The first level of guidelines for designing table and data structures in a relational database. The first normal form guideline recommends creating a unique key for every row in a database table, eliminating duplicate columns from a table, and creating separate tables to contain related data. A database that follows these guidelines is said to be in first normal form.

2NF

The second level of guidelines for designing table and data structures in a relational database. The second-normal-form guideline incorporates the guidelines of first normal form; in addition, it recommends removing data that applies to multiple rows in a table into its own table and using a foreign key to create a relationship to the original table. A database that follows these guidelines is said to be in second normal form.

3D feature

A representation of a three-dimensional, real-world object in a map or scene, with elevation values (z-values) stored within the feature's geometry. Besides geometry, 3D features may have attributes stored in a feature table. In applications such as CAD, 3D features are often referred to as 3D models.

3D graphic

A representation of a three-dimensional, real-world object in a map or scene, with elevation values (z-values) stored within the feature's geometry. Unlike 3D features, 3D graphics do not have attributes.

3D model

A construct used to portray an object in three dimensions. In GIS, 3D models are often referred to as 3D features.

3D multipatch

In ArcGIS, a type of geometry comprised of planar three-dimensional rings and triangles, used in combination to model objects that occupy discrete area or volume in three-dimensional space. Multipatches may represent geometric objects like spheres and cubes, or real-world objects like buildings and trees.

3D polygon

A three-dimensional object or volume defined by a number of plane faces or polygons.

3D scene

In the ArcGIS 3D Analyst extension and ArcView 3.x, a document type that is used to display three-dimensional data. It consists of a table of contents and a display area called a viewer. The viewer has a control bar with buttons and tools that can adjust the display of 3D data and identify and select features. A 3D scene may contain multiple viewers showing the same data from different perspectives.

3D shape

A point, line, or polygon that stores x-, y-, and z-coordinates as part of its geometry. A point has one set of z-coordinates; lines and polygons have z-coordinates for each vertex in a shape.

3D style

In ArcScene and ArcGlobe, a library containing 3D symbols.

3D symbol

A symbol with properties that allow it to be rendered in three dimensions.

3NF

The third level of guidelines for designing table and data structures in a relational database. The third-normal-form guideline incorporates the guidelines of first and second normal form; in addition, it recommends removing from a table those columns that do not depend on the table's primary key. A database that follows these guidelines is said to be in third normal form.

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A

abbreviation

A shortened form of a word or phrase which represents the whole. Abbreviations are commonly a letter or group of letters taken from the complete form of the word, such as the usage of St. in place of Street.

Abbreviation Dictionary

In Maplex for ArcGIS, a file that contains whole words and their abbreviated forms to allow automated shortening of labels.

abscissa

In a rectangular coordinate system, the distance of the x-coordinate along a horizontal axis from the vertical or y-axis. For example, a point with the coordinates (7,3) has an abscissa of 7.

absolute accuracy

The degree to which the position of an object on a map conforms to its correct location on the earth according to an accepted coordinate system.

absolute coordinates

Coordinates that are referenced to the origin of a given coordinate system.

absolute mode

A way of using a digitizing tablet in which locations on the tablet are mapped to specific locations on the screen. Moving the digitizer puck on the tablet surface causes the screen pointer to move to precisely the same position on the screen.

absolutely constrained adjustment

In Survey Analyst for field measurements, one of two possibilities for performing a constrained adjustment. In the absolutely constrained adjustment, the coordinates of the reference points keep their original value. Use this method when reference points should remain unchanged in the survey dataset.

absorption

The amount of electromagnetic energy lost through interactions with gas molecules and matter during its passage through the atmosphere.

abstract class

In ArcObjects, a specification for subclasses that is often shown on object model diagrams to help give structure to the diagram. An abstract class is not defined in a type library and cannot be instantiated.

abstraction

A simplified idea of a real-world object or system.

access control list

A list of accounts or users used to designate restricted and unrestricted services and the authentication criteria required to access an object.

access key

A keyboard shortcut that allows a user to access the contents of the Main menu by holding down the Alt key and pressing the underlined letter on the menu or menu command item. An access key is created by placing an ampersand (&) in front of the appropriate letter in the command's caption.

accessibility

An aggregate measure of the degree of ease with which a place, person, or thing can be reached, depending on factors such as slope, traffic, distance, and so on.

Account Info Web Service

A SOAP ArcWeb service used to view information about ArcWeb Services accounts such as usage statistics on data services and ArcWeb services. Account Info Web Service is available as a SOAP interface and a Web interface.

accuracy

The degree to which a measured value conforms to true or accepted values. Accuracy is a measure of correctness. It is distinguished from precision, which measures exactness.

acetate

In ArcWeb Services, circles, lines, polygons, points, or markers that become transparent when not active. Acetate features are overlaid on other map layers and can be independently annotated.

acknowledgment file|acknowledgement file

In ArcGIS, an XML file that contains an acknowledgement message.

acknowledgment message|acknowledgement message

In ArcGIS, a message from a replica to its relative acknowledging the data changes received by the sending replica.

ACL

Acronym for access control list. A list of accounts or users used to designate restricted and unrestricted services and the authentication criteria required to access an object.

across-track scanner

A remote-sensing tool with an oscillating mirror that moves back and forth across a satellite's direction of travel, creating scan line strips that are contiguous or that overlap slightly, thereby producing an image.

active data frame

The data frame currently being worked on—for example, the data frame to which layers are being added. The active data frame is highlighted on the map, and its name is shown in bold text in the table of contents.

active network

In Survey Analyst for field measurements, the focus of the analyses applied. In an active network, users may list a network's datum points in the Survey Explorer, detect and solve breaks in the network's computation sequence, and find and repair cycles in the network.

active remote sensing

A remote-sensing system, such as radar, that produces electromagnetic radiation and measures its reflection back from a surface.

Active Server Pages

A Microsoft server-side scripting technology that can be used to create and run dynamic, interactive Web applications, which are typically coded in JScript, JavaScript or VBScript. An ASP file contains not only the text and HTML tags that standard Web documents contain, but also commands written in a scripting language, which can be carried out on the server or the client.

Active Template Library

A set of C++ template classes, developed by Microsoft for use in building Windows COM objects.

active theme

In ArcView 3.x, the theme in a view document to which button and tool actions or corresponding menu commands are applied. An active theme appears raised in a view's table of contents.

ActiveX Connector

A type of ArcIMS Application Server Connector that is a Component Object Model (COM) dynamic link library (DLL) which can be used in a COM application such as Microsoft Active Server Pages (ASP).

acutance

A measure, using a microdensitometer or other instrument, of how well a photographic system shows sharp edges between contiguous bright and dark areas.

Add ArcWeb Data

An ArcWeb Services tool that allows ArcWeb data to be added to ArcGIS. Add ArcWeb Data is available as part of ArcWeb Toolbar for ArcGIS.

add-in

An extension to a software program that performs a custom task. ESRI provides various developer add-ins as part of the ArcGIS developer kit.

address

A designation of the location of a person's residence or workplace, an organization, or a building, consisting of numerical and text elements such as a street number, street name, and city arranged in a particular format.

address data

Data that contains address information used for geocoding. Address data may consist of one individual address or a table containing many addresses.

address data format

The arrangement of address information in a database, most often consisting of such address elements as house number, street direction, street name, street type, city, and postal code.

address data model

The rules of a geodatabase designed specifically to accommodate address-related material, such as streets, zones, ranges, and so forth. These rules define the address elements, their attribute values, and the relationships between them. An address data model facilitates address data storage.

address element

One of the components that comprise an address. House numbers, street names, street types, and street directions are examples of address elements.

address event

In ArcGIS, features that can be located based on address matching with a street network or other address identifier, such as ZIP Codes or lot numbers.

address event table

In ArcGIS, a table containing addresses but no spatial reference information. Using GIS software, address event tables can be geocoded to create a spatial data layer.

address field

A column in a table that stores one or some address elements. An address field can be present in reference data, address data, or both.

Address Finder Web Service

A SOAP ArcWeb service used to find geographical coordinates of an address and to find an address based on geographical coordinates.

address format

The particular structure and arrangement of address elements and a corresponding method of matching that can be used for a specific application. The address format may vary based on locale or country.

address geocoding

A GIS operation for converting street addresses into spatial data that can be displayed as features on a map, usually by referencing address information from a street segment data layer.

address locator

A dataset in ArcGIS that stores the address attributes, associated indexes, and rules that define the process for translating nonspatial descriptions of places, such as street addresses, into spatial data that can be displayed as features on a map. An address locator contains a snapshot of the reference data used for geocoding, and parameters for standardizing addresses, searching for match locations, and creating output. Address locator files have a .loc file extension. In ArcGIS 8.3 and previous versions, an address locator was called a geocoding service.

address locator property

A parameter in an address locator that defines the process of geocoding.

address locator style

A template on which an address locator is built. Each template is designed to accommodate a specific format of address and reference data, and geocoding parameters. The address locator style template file has a .lot file extension.

Address Manager Web Service

A SOAP ArcWeb service used to batch geocode a custom set of point addresses. Address Manager Web Service is available as a SOAP interface and a Web interface.

address matching

A process that compares an address or a table of addresses to the address attributes of a reference dataset to determine whether a particular address falls within an address range associated with a feature in the reference dataset. If an address falls within a feature's address range, it is considered a match and a location can be returned.

address range

Street numbers running from lowest to highest along a street or street segment. Address ranges are generally stored as fields in the attribute table of a street data layer. They often indicate ranges on the left and right sides of streets.

address service

A service that can determine the x,y location of an address, and return the address of an x,y location.

address standardization

The process of breaking down an address into elements and converting those elements with standard abbreviations or spellings. For best practices, this process applies to preparing the reference data and address data for matching.

address standardizer

A tool that prepares and breaks down an address into elements that can be used for geocoding. The process may translate some elements into standard keywords or abbreviations; for example, ""Avenue"" may be translated to ""Ave.""

address style

A set of guidelines that define the format of addresses and methods of matching that can be used for a specific application.

adds table

The geodatabase system table, created when a feature class or table is registered as versioned, that maintains information on all rows that have been inserted or updated.

ADF

Acronym for Application Developer Framework. The set of custom Web controls and templates that can be used to build Web applications that communicate with a GIS server. ArcGIS Server includes an ADF for both .NET and Java.

ADF runtime

The components required to run an application built with the ADF.

adjacency

A type of spatial relationship in which two or more polygons share a side or boundary.

adjacency query

A statement or logical expression used to select geographic features that share a boundary.

adjustment level

In Survey Analyst for cadastres, a number that corresponds to a specific set of displacement vectors in a series of adjustments to the cadastral fabric. The adjustment level is generally identified by the date and time of the adjustment.

adoption

The process of appropriating a technology and putting it into use for one's own purposes; the act by an individual, organization, or community of choosing a technology and putting it into effect.

ADT

Acronym for abstract data type. For OpenLS, a data type and structure for location information that is shared by two or more services. ADTs are application schemas that are encoded in XML for location services (XLS).

Advanced Very High Resolution Radiometer

A scanner flown on National Oceanic and Atmospheric Administration (NOAA) polar-orbiting satellites for measuring visible and infrared radiation reflected from vegetation, cloud cover, shorelines, water, snow, and ice. AVHRR data is often used for weather prediction and vegetation mapping.

aerial photograph

A photograph of the earth's surface taken from a platform flying above the surface but not in orbit, usually an aircraft. Aerial photography is often used as a cartographic data source for basemapping, locating geographic features, and interpreting environmental conditions.

affiliation

In MOLE, the type of threat posed by the war fighting element being represented. The four basic types supported by MOLE are unknown, friend, neutral, and hostile.

affine transformation

A geometric transformation that scales, rotates, skews, and/or translates images or coordinates between any two Euclidean spaces. It is commonly used in GIS to transform maps between coordinate systems. In an affine transformation, parallel lines remain parallel, the midpoint of a line segment remains a midpoint, and all points on a straight line remain on a straight line.

agent

In modeling, an entity within a model that conducts transactions to simulate the actions of a human, group of humans, animal, or other actor.

agent-based model

A simulation of the large-scale consequences of the decisions and interactions of individual members of a population. An agent-based model consists of an environment or framework that defines the scope and rules of actions, along with a number of agents representing one or more actors whose parameters and behaviors are defined. When the model is run, the characteristics of each agent are tracked through time and space.

aggregation

The process of collecting a set of similar, usually adjacent, polygons (with their associated attributes) to form a single, larger entity.

AIR

Acronym for Adobe Integrated Runtime. A cross-platform runtime environment built on HTML, Flash, and Flex. AIR applications are deployed on a desktop and can communicate with a server for updates or extended functionality.

air station

In aerial photography, each point in the flight path at which the camera exposes the film.

AIXM

Acronym for Aeronautical Information Exchange Format. An XML format used to describe aeronautical data transactions created and maintained by EUROCONTROL (European Organisation for the Safety of Air Navigation), in the process of being adopted worldwide.

AJAX

Acronym for Asynchronous JavaScript and XML. A programming technique for creating fast, interactive Internet applications. AJAX adds a small application to part of the software user's browser for fast loading and display.

albedo

A measure of the reflectivity of an object or surface; the ratio of the amount of radiation reflected by a body to the amount of energy striking it.

alert

A message that calls attention to a notable situation or informs users of changes in the state of a monitored situation.

algorithm

A mathematical procedure used to solve problems with a series of steps. Algorithms are usually encoded as a sequence of computer commands.

alias

An alternative name specified for fields, tables, files, or datasets that is more descriptive and user-friendly than the actual name. On computer networks, a single e-mail alias may refer to a group of e-mail addresses.

aliasing

The jagged appearance of curves and diagonal lines in a raster image. Aliasing becomes more apparent as the size of the raster pixels is increased or the resolution of the image is decreased.

alidade

A peep sight mounted on a straightedge and used to measure direction.

align fields

A task that identifies the fields required for geocoding, such as address and city, when uploading data.

aligned dimension

A drafting symbol that runs parallel to the baseline and indicates the true distance between beginning and ending dimension points.

allocation

In network analysis, the process of assigning entities or edges and junctions to features until the feature's capacity or limit of impedance is reached. For example, streets may be assigned to the most accessible fire station within a six-minute radius, or students may be assigned to the nearest school until it is full.

almanac

In GPS, a file transmitted from a satellite to a receiver that contains information about the orbits of all satellites included in the satellite network. Receivers refer to the almanac to determine which satellite to track.

along-track scanner

A remote-sensing tool with a line of many fixed sensors that record reflected radiation from the terrain along a satellite's direction of movement, creating scan-line strips that are contiguous or that overlap slightly, thereby producing an image.

alphanumeric grid

A grid of numbered rows and lettered columns (or vice versa) superimposed on a map, used to find and identify features. Alphanumeric grids are commonly used as a reference system on local street maps.

alternate key

An attribute or set of attributes in a relational database that provides a unique identifier for each record and could be used as an alternative to the primary key.

alternate name

A name for an address element, usually a street name, that is different from the official or most common name. For example, a highway number might be an alternate name for a street name.

altitude

The height or vertical elevation of a point above a reference surface. Altitude measurements are usually based on a given reference datum, such as mean sea level.

AM/FM

Acronym for automated mapping/facilities management. GIS or CAD-based systems used by utilities and public works organizations for storing, manipulating, and mapping facility information such as the location of geographically dispersed assets.

ambiguity

In GIS, a state of uncertainty in data classification that exists when an object may appropriately be assigned two or more values for a given attribute. For example, coastal areas experiencing tidal fluctuations may be dry land at some times and under water at other times. Ambiguity may be caused by changeable conditions in reality, by incomplete or conflicting definitions of attributes, or by subjective differences in the evaluation of data. It may also be caused by disputes, as when two parties claim ownership of the same tract of land.

American National Standards Institute

The private, nonprofit organization that develops U.S. industry standards through consensus and public review.

American Standard Code for Information Interchange

The de facto standard for the format of text files in computers and on the Internet that assigns a 7-bit binary number to each alphanumeric or special character. ASCII defines 128 possible characters.

AML

Acronym for ARC Macro Language. A proprietary, high-level programming language created by ESRI for generating end-user applications in ArcInfo Workstation.

amoeba

An area calculated by finding the outermost customers of a store along several vectors and connecting them. Complex market areas are more accurate than simple market areas because they respond to physical and cultural barriers. They are sometimes called amoebas because of their irregular shapes.

anaglyph

A stereo image made by superimposing two images of the same area. The images are displayed in complementary colors, usually red and blue or green. When viewed through filters of corresponding colors, the images appear as one three-dimensional image.

analog

Represented continuously rather than in discrete steps; having value at any degree of precision.

analog image

An image represented by continuous variation in tone, such as a photograph.

analysis

A systematic examination of a problem or complex entity in order to provide new information from what is already known.

analysis extent

The geographic bounding area within which spatial analysis will occur. The bounding area is set by defining the x,y coordinates of opposite corners, usually the bottom-left and top-right corners of results.

analysis mask

In digital cartography, a means of covering or hiding features on a map to enhance cartographic representation. For example, masking is often used to cover features behind text to make the text more readable.

analysis of variance

A statistical procedure used to evaluate the variance of the mean values for two or more datasets in order to assess the probability that the data comes from the same sample or statistical population.

ancillary data

In digital image processing, data from sources other than remote sensing, used to assist in analysis and classification or to populate metadata.

ancillary source

A supplementary source of information.

angular unit

The unit of measurement on a sphere or a spheroid, usually degrees. Some map projection parameters, such as the central meridian and standard parallel, are defined in angular units.

animation

In ArcMap, ArcScene, and ArcGlobe, a collection of animation tracks that define the dynamic property changes to associated objects. An animation allows for navigation through the display, visualization of temporal changes, or alteration of layer and scene properties, such as layer transparency or the scene background.

Animation Manager

In ArcMap, ArcScene, and ArcGlobe, the interface in which the keyframes, tracks and time-scale properties of an animation can be edited and an animation can be timed and previewed.

anisotropic

Having nonuniform spatial distribution of movement or properties, usually across a surface.

anisotropy

A property of a spatial process or data in which spatial dependence (autocorrelation) changes with both the distance and the direction between two locations.

annotation

In cartography, text or graphics on a map that provide information for the map reader. Annotation may identify or describe a specific map entity, provide general information about an area on the map, or supply information about the map itself.

annotation class

A subset of annotation in a standard or feature-linked geodatabase annotation feature class that contains properties that determine how the subset of annotation will display. A standard or feature-linked geodatabase annotation feature class may contain one or more annotation classes.

annotation construction method

One of a number of procedures that dictate what type of annotation feature is created and the number of points required to create new annotation features. Construction methods include horizontal, straight, curved, leader line, and follow feature.

annotation feature class

A geodatabase feature class that stores text or graphics that provide information about features or general areas of a map (annotation). An annotation feature class may be linked to another feature class, so that edits to the features are reflected in the corresponding annotation (feature-linked annotation). Annotation in a geodatabase is edited during an edit session, using the tools on the Annotation toolbar.

annotation group

A container within a map document for organizing and managing text or graphics that provide additional information about features or general areas of a map. Annotation groups allow control of the display of different sets of annotation. Annotation stored in a map document is edited with the tools on the Drawing toolbar.

annotation layer

A layer that references annotation. Information stored for annotation includes a text string, a position at which it can be displayed, and display characteristics.

annotation target

In ArcMap, the annotation group or feature class in a map document where new annotation will be stored when created when using the New Text tools on the Draw toolbar or when copying and pasting annotation. Annotation created with the Annotation Edit tools is stored in the current Editing target, not in the annotation target.

ANOVA

A statistical procedure used to evaluate the variance of the mean values for two or more datasets in order to assess the probability that the data comes from the same sample or statistical population.

ANSI

Acronym for American National Standards Institute. The private, nonprofit organization that develops U.S. industry standards through consensus and public review.

Ant

An open-source, Java-based tool from the Apache Software Foundation that is used to manage the build procedure of applications.

antipode

Any point on the surface of a sphere that lies 180 degrees (opposite) from a given point on the same surface, so that a line drawn between the two points through the center of the sphere forms a true diameter.

any-vertex connectivity

In network datasets, a type of edge connectivity policy that states that an edge may connect to another edge or junction where they have coincident vertices.

anywhere fix

A position that a GPS receiver can calculate without knowing its own location or the local time.

AOI

The extent used to define a focus area for either a map or database production.

apartment

In Microsoft's COM component programming model, a group of threads, working within a process, that work within the same context.

aphylactic projection

A projection that does not have equal area, conformal, or equidistant characteristics. The compromise projection is an attempt at balance between these characteristics, and is often used in thematic mapping.

API

Acronym for application programming interface. A set of interfaces, methods, protocols, and tools that application developers use to build or customize a software program. APIs make it easier to develop a program by providing building blocks of prewritten, tested, and documented code that are incorporated into the new program. APIs can be built for any programming language.

API key

In ArcWeb Services, an encryption-based authentication method for the ArcWeb Explorer JavaScript API. An API key is valid only for registered URLs.

apogee

In an orbit path, the point at which the object in orbit is farthest from the center of the body being orbited.

APP-6A

A military symbology specification published by NATO (North Atlantic Treaty Organization). APP-6A is based on MIL-STD-2525A, the predecessor to MIL-STD-2525B.

appending

Adding features from multiple data sources of the same data type into an existing dataset.

applet

A small program that usually executes from within a Web browser. Applets are compatible with most platforms, and can also be used within applications or devices that support applets.

application

The use of a GIS to solve problems, automate tasks, or generate information within a specific field of interest. For example, a common agricultural application of GIS is determining fertilization requirements based on field maps of soil chemistry and previous crop yields.

Application Developer Framework

The set of custom Web controls and templates that can be used to build Web applications that communicate with a GIS server. ArcGIS Server includes an ADF for both .NET and Java.

application programming interface

A set of interfaces, methods, protocols, and tools that application developers use to build or customize a software program. APIs make it easier to develop a program by providing building blocks of prewritten, tested, and documented code that are incorporated into the new program. APIs can be built for any programming language.

application server

A computer program that receives user requests through a client application and returns results to the client.

application Web service

A Web service that solves a particular problem; for example, a Web service that finds all of the hospitals within a certain distance of an address. An application Web service can be implemented using the native Web service framework of a Web server; for example, an ASP.NET Web service (WebMethod) or Java Web service (Axis).

arbitrary symbol

A symbol that has no visual similarity to the feature it represents—for example, a circle used to represent a city, or a triangle used to represent a school.

arc

On a map, a shape defined by a connected series of unique x,y coordinate pairs. An arc may be straight or curved.

ARC Macro Language

A proprietary, high-level programming language created by ESRI for generating end-user applications in ArcInfo Workstation.

arc second

An angle equal to one sixtieth of a minute of latitude or longitude.

ArcGIS Online

A set of web-based base maps, globes and other data and services created by ESRI for use inside ArcGIS products and GIS applications on the Internet.

ArcGIS Server Web service

A Web service processed and executed from within an ArcGIS server. Each Web service has a distinct HTTP location (URL). Web access is enabled by default for all ArcGIS Server services, but can be turned off by an administrator.

ArcGIS Spatial Analyst

An ArcGIS extension that provides spatial modeling and analysis features. It allows the creation, querying, mapping, and analysis of cell-based raster data and integrated vector-raster analysis.

arcgisant

The command, provided with the Java ADF, that starts the Apache Ant tool that builds and deploys Web applications.

architecture

The internal design of an application or software package; the way software or hardware components are organized into a functioning unit.

archive

A collection of information or data that is stored on a permanent medium such as CDs, discs, or tapes. Information is archived to ensure its security or persistence.

archiving

In ArcGIS and ArcSDE, a procedure that allows a geodatabase to capture and store updates to features and records as the version is posted or edits are saved directly. Archiving builds a lineage of historical information that can be viewed and queried.

ArcIMS

ESRI software that allows for centrally hosting and serving GIS maps, data, and applications for use on the Internet. The administrative framework lets users author configuration files, publish maps, design Web pages, and administer ArcIMS spatial servers. ArcIMS supports Windows, Linux, and UNIX platforms and is customizable on many levels.

ArcIMS Administrator

The ArcIMS component that allows users to manage ArcIMS services, servers, virtual servers, and folders.

ArcIMS application server

The ArcIMS component that handles the distribution of incoming requests. It tracks which services are running on which ArcIMS spatial servers and hands off a request to the appropriate ArcIMS spatial server.

ArcIMS Application Server Connector

A component used to connect the Web server to the ArcIMS application server. Types of connectors include ActiveX Connector, ColdFusion Connector, Java Connector, .NET Link, and Servlet Connector. Connectors must be installed on the same computer as the Web server.

ArcIMS architecture

A multitier framework that includes ArcIMS components: the ArcIMS Manager/manager applications, application server, application server connectors, monitor, tasker, spatial servers, and viewers. The complete architecture also includes a Windows or UNIX operating system, a Web server, a servlet engine, and client-side Web browsers.

ArcIMS Author

The ArcIMS component that allows users to organize data into a configuration file that can be used to create a service. A configuration file specifies the map content: which data layers will be displayed and how they will look (color, symbols, labels, etc.).

ArcIMS Designer

The ArcIMS component that guides users in designing Web pages based on at least one service and one of the ArcIMS viewers. Users choose from a variety of options including toolbar functions, scale bar properties, and visible layer settings.

ArcIMS Manager

A suite of Web pages, deprecated in the 9.0 release, that guides users through the process of authoring configuration files, publishing services, designing Web pages, and administering sites. ArcIMS Manager combines the three independent applications (ArcIMS Author, ArcIMS Designer, and ArcIMS Administrator) into one wizard-driven framework. ArcIMS Manager resides on the Web server computer and can be accessed remotely. It is also referred to as the Web-based Manager and Remote Manager.

ArcIMS manager application

Any one of these stand-alone applications: ArcIMS Author, ArcIMS Administrator, or ArcIMS Designer. Each of these applications guides users through a process: authoring configuration files (ArcIMS Author), creating services and administering sites (ArcIMS Administrator), or designing Web pages (ArcIMS Designer).

ArcIMS Monitor

An ArcIMS component that tracks the state of the ArcIMS spatial server. When a computer system reboots, ArcIMS Monitor restarts services automatically by restarting the site configuration. This configuration is based on the setting saved in a serialized file ending in the file extension .sez.

ArcIMS service

A service that allows the content of a configuration file to be published on the Internet. The configuration file provides data layer content and symbology that the service registers to the ArcIMS spatial server and Web server for processing.

ArcIMS Service Administrator

A Web-based administration application that allows users to manage ArcIMS services and ArcSDE services remotely.

ArcIMS Tasker

An ArcIMS component that removes temporary image files generated by the image and ArcMap image services at a user-defined time interval.

ArcIMS viewer

Any one of the three Web site designs that come as standard options in ArcIMS Designer: the HTML, Java Custom, and Java Standard. They provide the functionality and graphic look for Web sites. The Java viewers require a one-time Web download and are only compatible with Web browsers that support Java 2 plug-in functionality.

ArcIMS virtual server

A grouping of one or more spatial servers into a single unit for administrative purposes. All of the following are ArcIMS virtual servers: the ArcMap server, extract server, feature server, geocode server, image server, metadata server, query server, and route server. The ArcMap server and route server are optional extensions to ArcIMS.

ArcIMS Web site directory

The directory that stores the files that make up the ArcIMS Internet GIS application and other files. It is the directory specified as the Working Directory during the installation process. The default location for Windows is C:\ArcIMS. The default location for UNIX is $home.

ArcIMSFolders.sez

A serialization file containing ArcIMS folders and any submitted MapNotes and EditNotes. It is stored in the ArcIMS AppServer directory. This file replaces the EsriMapCookies.ser file used in ArcIMS 3.1.

ArcIMSSite.sez

A serialization file created in the ArcIMS AppServer directory that saves site parameters, including which services are running and which servers are started. This file replaces the EsriMapCatalog.ser file used in ArcIMS 3.1.

ArcInfo interchange file

A file format, also known as an export file, used to enable a coverage, grid or TIN and an associated INFO table to be transferred between different machines which are not connected by any type of file sharing network. ArcInfo interchange files have a .E00 extension, which increments to .E01, .E02, and so on, if the interchange file is composed of several separate files.

ArcInfo workspace

A file-based collection of coverages, grids, TINs, or shapefiles stored as a directory of folders in the file system.

ArcMap Server

A public ArcIMS virtual server that allows an ArcGIS user to create maps in ArcMap, rather than ArcIMS Author or ArcIMS Manager, and publish them on the Internet. The ArcMap server is an optional extension to ArcIMS.

arc-node topology

The data structure in a coverage used to represent linear features and polygon boundaries and to support analysis functions, such as network tracing. Nodes represent the beginning and ending vertices of each arc. Arcs that share a node are connected, and polygons are defined by a series of connected arcs. An arc that intersects another arc is split into two arcs. Each arc that defines all or part of a polygon boundary records the number of the polygon to its left and to its right, giving it a direction of travel.

ArcObjects

A library of software components that make up the foundation of ArcGIS. ArcGIS Desktop, ArcGIS Engine, and ArcGIS Server are all built using the ArcObjects libraries.

ArcSDE

Technology for managing geographic information in a relational database management system (RDBMS). ArcSDE is part of the ArcGIS platform, and is the data server between ArcGIS and relational databases. It is widely used to enable geographic information to be shared by many users across a network and to scale in size from personal, to workgroup, to enterprise use.

ArcSDE administrative user

The user who administers ArcSDE geodatabases. The ArcSDE administrative user can be the SDE user, but for DBO-schema ArcSDE geodatabases in SQL Server it is any user whose login is mapped to DBO in the database, and for user-schema geodatabases in Oracle, the ArcSDE administrative user is the user in whose schema the geodatabase is stored.

ArcSDE client application

An application or program that communicates with ArcSDE to query, store and manage spatial data. Examples include ArcGIS Desktop, ArcGIS Server, and ArcIMS.

ArcSDE database server

In ArcCatalog, an instance of SQL Server Express used to store ArcSDE geodatabases.

ArcSDE geodatabase

A geodatabase stored in an RDBMS served to client applications using ArcSDE technology. An ArcSDE geodatabase can support long transactions and versioned workflows, be used as a workspace for geoprocessing tasks, and provide the benefits of a relational database such as security, scalability, backup and recovery, and SQL access.

ArcSDE Personal Edition geodatabase

A single-user ArcSDE geodatabase that is created on Microsoft SQL Server Express.

ArcSDE system tables

A collection of tables that store metadata about user tables in a geodatabase managed using ArcSDE technology. ArcSDE system tables are owned by an ArcSDE administrative user.

ArcSDE Workgroup Edition geodatabase

A Microsoft SQL Server Express database that uses ArcSDE technology to store, query, and modify spatial data. Workgroup geodatabases accept up to 10 non-Web client connections and unlimited Web client connections to the SQL Server Express instance and are licensed through ArcGIS Server Workgroup edition.

ArcToolbox

A user interface in ArcGIS used for accessing, organizing, and managing a collection of geoprocessing tools, models, and scripts.

ArcToolbox Window

A dockable window used to display, manage, and use the contents of toolboxes in ArcGIS. It provides a shortcut to frequently used tools contained within toolboxes that may be stored in folders or geodatabases on disk.

ArcView project

In ArcView 3, a file for creating and storing documents for GIS work. All activity in ArcView 3 takes place within project files, which use five types of documents to organize information: views, tables, charts, layouts, and Avenue scripts. A project file organizes its documents and stores their unique settings in an ASCII format file with the extension .apr.

ArcView project file

In ArcView 3, a file for creating and storing documents for GIS work. All activity in ArcView 3 takes place within project files, which use five types of documents to organize information: views, tables, charts, layouts, and Avenue scripts. A project file organizes its documents and stores their unique settings in an ASCII format file with the extension .apr.

ArcWeb Explorer

The client-side API of ArcWeb Services. It is based on Adobe Flex, a cross-platform development framework for creating rich Internet applications. Developers can use the ArcWeb Explorer Flex API, the JavaScript to Flex Bridge, or the JavaScript API to create their own applications. </SPAN>ArcWeb Explorer is sometimes used to refer to the customizable demo application.

ArcWeb Mobile Toolkit

A J2ME-based toolkit for building mobile applications that use ArcWeb Services.

ArcWeb Services

ESRI-hosted Web services that include map data and on-demand geospatial capabilities needed to add real-time locations, addresses, points of interest, dynamic maps, and routing directions to Web and wireless applications.

ArcWeb Services account

A Web site for accessing information about an ArcWeb account. This site allows users to activate an ArcWeb Services account, view usage of ArcWeb services, manage POI and address records, and manage groups and alerts.

ArcWeb site

An ESRI Web site for building custom services, using applications, and learning about ArcWeb Services.

ArcXML

Acronym for Arc Extensible Markup Language. A file format that provides a structured method for communication between all ArcIMS components. ArcXML defines content for services and is used for requests and responses between clients, the business logic tier, and servers.

are

A metric areal unit of measure equal to 100 square meters. One are is equal to 1,076.39 square feet, or 0.025 acres.

area

A closed, two-dimensional shape defined by its boundary or by a contiguous set of raster cells.

area chart

A chart that emphasizes the difference between two or more groups of data; for example, the changes in a population from one year to the next. The area of interest is usually shaded in a solid color.

area of adjustment

In Survey Analyst - Cadastral Editor, a continuous set of parcels that have been selected for adjustment by least-squares.

area of interest

The extent used to define a focus area for either a map or database production.

areal scale

The ratio or relationship between a distance or area on a map and the corresponding distance or area on the ground, commonly expressed as a fraction or ratio. A map scale of 1/100,000 or 1:100,000 means that one unit of measure on the map equals 100,000 of the same unit on the earth.

argument

In computing, a value or expression passed to a function, command, or program.

arithmetic expression

A number, variable, function, or combination of these, with operators or parentheses, or both, that can be evaluated to produce a single number.

arithmetic function

A type of mathematical function that performs a calculation on the values of cells in an input raster. There are six arithmetic functions in ArcGIS Spatial Analyst: Abs, Int, Float, Round up (Ceil), Round down (Floor) and Negate.

arithmetic operator

The symbolic representation of a process or operation performed against one or more operands in an expression, such as ""+"" (plus, or addition) and "">"" (greater than). When evaluated, operators return a value as their result. If multiple operators appear in an expression, they are evaluated in order of their operator precedence.

array

In computing, a fundamental data structure consisting of a variable with multiple, sequentially indexed, cells that can each store a value of the same type. Each cell of the array acts as a variable, and the cells are referenced by an index value for each array dimension. One-dimensional arrays, called vectors, and two-dimensional arrays, called matrices, are most common, but arrays may have more dimensions.

artificial neural network

A computer architecture modeled after the human brain and designed to solve problems that human brains solve well, such as recognizing patterns and making predictions from past performance. Neural networks are composed of interconnected computer processors that calculate a number of weighted inputs to generate an output. For example, an output might be the approval or rejection of a credit application. This output would be based on several inputs, including the applicant's income, current debt, and credit history. Some of these inputs would count more than others; cumulatively, they would be compared to a threshold value that separates approvals from rejections. Neural networks ""learn"" to generate better outputs by adjusting the weights and thresholds applied to their inputs.

ascending node

The point at which a satellite traveling south to north crosses the equator.

ASCII

Acronym for American Standard Code for Information Interchange. The de facto standard for the format of text files in computers and on the Internet that assigns a 7-bit binary number to each alphanumeric or special character. ASCII defines 128 possible characters.

ASP

Acronym for Active Server Pages. A Microsoft server-side scripting technology that can be used to create and run dynamic, interactive Web applications, which are typically coded in JScript, JavaScript or VBScript. An ASP file contains not only the text and HTML tags that standard Web documents contain, but also commands written in a scripting language, which can be carried out on the server or the client.

ASP.NET

A Microsoft-created programming framework built on top of the common language runtime (CLR) that can be used on a Windows server to create Web applications in a variety of programming languages.

aspatial data

Data without inherently spatial qualities, such as attributes.

aspatial query

A request for records of features in a table based on their attribute values.

aspect

The compass direction that a topographic slope faces, usually measured in degrees from north. Aspect can be generated from continuous elevation surfaces. For example, the aspect recorded for a TIN face is the steepest downslope direction of the face, and the aspect of a cell in a raster is the steepest downslope direction of a plane defined by the cell and its eight surrounding neighbors.

aspect ratio

The ratio of the width of an image to its height. The aspect ratio of a standard computer monitor is 4:3 (rectangular).

assembly

A package of software and its associated resources. For example, an ArcGIS Win32 assembly will typically include executables, DLLs, object libraries, registry files, and help files for a unit of software.

assignment operator

A type of operator that assigns the result of an expression to an output, usually a raster, for storage.

associated feature class

In Survey Analyst - Cadastral Editor, a feature class that uses the cadastral fabric as a basemap, and has been associated with cadastral fabric. Associated feature classes can be corrected to maintain alignment with cadastral fabric parcels after least-squares adjustments of the cadastral fabric.

association

In UML, the relationship between two classes. In an association, instances of the classes in question usually exist together, but can exist on their own.

assumed bearing

A bearing measured from an arbitrarily chosen reference line called an assumed meridian.

astrolabe

An instrument that measures the vertical angle between a celestial body and the horizontal plane at an observer's position. The astrolabe was replaced by the sextant in the fifteenth century for navigation, but modern versions are still used to determine local time and latitude.

asynchronous

Not synchronous; that is, not occurring together or at the same time.

asynchronous request

In programming, a set of actions or events that may occur simultaneously. For example a program that launches another program, then continues execution while the other program is still running is said to be asynchronous.

ATL

Acronym for Active Template Library. A set of C++ template classes, developed by Microsoft for use in building Windows COM objects.

atlas

A collection of maps usually related to a particular area or theme and presented together. Examples of atlases include world atlases, historical atlases, and biodiversity atlases.

atlas grid

A grid of numbered rows and lettered columns (or vice versa) superimposed on a map, used to find and identify features. Alphanumeric grids are commonly used as a reference system on local street maps.

atmospheric window

Parts of the electromagnetic spectrum that can be transmitted through the atmosphere with relatively little interference.

atomic clock

A clock that keeps time by the radiation frequency associated with a particular atomic reaction. Atomic clocks are used in official timekeeping.

attenuation

The dimming and blurring effects in remotely sensed images caused by the absorption and scattering of light or other radiation that passes through the earth's atmosphere.

attractiveness

A measure of the combined attributes of a center or site that are considered positive features or that draw in potential customers or tenants.

attribute

Nonspatial information about a geographic feature in a GIS, usually stored in a table and linked to the feature by a unique identifier. For example, attributes of a river might include its name, length, and sediment load at a gauging station.

attribute data

Tabular or textual data describing the geographic characteristics of features.

attribute domain

In a geodatabase, a mechanism for enforcing data integrity. Attribute domains define what values are allowed in a field in a feature class or nonspatial attribute table. If the features or nonspatial objects have been grouped into subtypes, different attribute domains can be assigned to each of the subtypes.

attribute key

An attribute or set of attributes in a database that uniquely identifies each record. A primary key allows no duplicate values and cannot be null.

attribute query

A request for records of features in a table based on their attribute values.

attribute table

A database or tabular file containing information about a set of geographic features, usually arranged so that each row represents a feature and each column represents one feature attribute. In raster datasets, each row of an attribute table corresponds to a certain zone of cells having the same value. In a GIS, attribute tables are often joined or related to spatial data layers, and the attribute values they contain can be used to find, query, and symbolize features or raster cells.

attributes dialog box

In ArcMap, a dialog box that displays attributes of selected features for editing.

attribution

The process of assigning attributes to features.

authalic projection

A projection in which the whole of the map as well as each part has the same proportional area as the corresponding part of the earth. An equal-area projection may distort shape, angle, scale, or any combination thereof. No flat map can be both equal-area and conformal.

authentication

The process of validating the identity of a user who logs on to a computer system, network, or Web site.

Authentication Web Service

A SOAP ArcWeb service used to validate access to ArcWeb Services.

authorization

Completion of the software registration process. During authorization, the single-use or server product and/or extensions have been installed and registered, and an authorization file has been generated through the appropriate registration wizard and sent to the software user.

authorization file

A file that contains single use or server product authorization data. Each authorization file contains information regarding the feature name, version number, time-out date, registration number, and authorization code.

autocorrelation

The correlation or similarity of values, generally values that are nearby in a dataset. Temporal data is said to exhibit serial autocorrelation when values measured close together in time are more similar than values measured far apart in time. Spatial data is said to exhibit spatial autocorrelation when values measured nearby in space are more similar than values measured farther away from each other.

automated cartography

The process of making maps using computer systems that carry out many of the tasks associated with map production.

automated digitizing

The creation of vector data from raster data through automated tracing of pixels that are in close proximity and of the same or similar value.

automated feature extraction

The identification of geographic features and their outlines in remote-sensing imagery through postprocessing technology that enhances feature definition, often by increasing feature-to-background contrast or using pattern recognition software.

automated mapping/facilities management

GIS or CAD-based systems used by utilities and public works organizations for storing, manipulating, and mapping facility information such as the location of geographically dispersed assets.

automated text placement

An operation in which text is automatically placed on or next to features on a digital map by a software application according to rules set by the software user.

automation

The automatic functioning of a machine, system, or process, without the need for human interaction.

automation scale

The scale at which nondigital data is made digital; for example, a map digitized at a scale of 1:24,000 has an automation scale of 1:24,000. The data can be rendered at different display scales.

autovectorization

The creation of vector data from raster data through automated tracing of pixels that are in close proximity and of the same or similar value.

availability

The degree of ease with which a dataset or other object may be found or obtained.

Avenue

The object-oriented programming language on which ArcView 3.x is based. Avenue provides tools for customizing ArcView 3.x and developing ArcView 3.x applications.

average point spacing

The average distance separating sample points in a point dataset. A terrain dataset uses the average point spacing of a dataset to define a horizontal tiling system into which to divide input source measurements.

AVHRR

Acronym for Advanced Very High Resolution Radiometer. A scanner flown on National Oceanic and Atmospheric Administration (NOAA) polar-orbiting satellites for measuring visible and infrared radiation reflected from vegetation, cloud cover, shorelines, water, snow, and ice. AVHRR data is often used for weather prediction and vegetation mapping.

AWS

ESRI-hosted Web services that include map data and on-demand geospatial capabilities needed to add real-time locations, addresses, points of interest, dynamic maps, and routing directions to Web and wireless applications.

AWX

The client-side API of ArcWeb Services. It is based on Adobe Flex, a cross-platform development framework for creating rich Internet applications. Developers can use the ArcWeb Explorer Flex API, the JavaScript to Flex Bridge, or the JavaScript API to create their own applications. ArcWeb Explorer is sometimes used to refer to the customizable demo application.

Axis

A Java-based toolkit for accessing SOAP Web services. Axis is developed by The Apache Software Foundation.

axis

A line along which measurements are made in order to determine the coordinates of a location.

azimuth

The horizontal angle, measured in degrees, between a baseline drawn from a center point and another line drawn from the same point. Normally, the baseline points true north and the angle is measured clockwise from the baseline.

azimuthal projection

A map projection that transforms points from a spheroid or sphere onto a tangent or secant plane. The azimuthal projection is also known as a planar or zenithal projection.

To the top

B

background

In ArcScene or ArcGlobe, the backdrop of the view. The color of the background can be set to suggest sky, empty space, or any color that improves visualization.

background image

A satellite image, aerial photograph, or scanned map over which vector data is displayed. Although a background image can be used to align coordinates, it is not linked to attribute information and is not part of the spatial analysis in a GIS.

backscatter

Electromagnetic energy that is reflected back toward its source by terrain or particles in the atmosphere.

backup

A copy of a file, a set of files, or a disk for safekeeping in case the original is lost or damaged.

BAM

Acronym for best available map. The most suitable data source for a map.

band

A set of adjacent wavelengths or frequencies with a common characteristic. For example, visible light is one band of the electromagnetic spectrum, which also includes radio, gamma, and infrared waves.

band ratio

A digital image-processing technique that enhances contrast between features by dividing a measure of reflectance for the pixels in one image band by the measure of reflectance for the pixels in the other image band.

band separate

An image format that stores each band of data in a separate file.

band-pass filter

A wave filter that allows signals in a certain frequency to pass through, while blocking or attenuating signals at other frequencies.

bandwidth

The amount of digital data that can be transferred over a computer network within a specified time period, usually measured in bits per second (bps).

bar scale

A map element used to graphically represent the scale of a map. A scale bar is typically a line marked like a ruler in units proportional to the map's scale.

barrier

In network analysis, an entity that prevents flow from traversing a network edge or junction.

base data

Map data over which other, thematic information is placed.

base height

In aerial photography, the height or altitude from which a photograph is taken.

base height ratio

In aerial photography, the distance on the ground between the centers of overlapping photos, divided by aircraft altitude. In a stereomodel, base height ratio is used to determine vertical exaggeration.

base layer

A data layer in a GIS to which all other layers are geometrically referenced.

base station

A GPS receiver at a known location that broadcasts and collects correction information for roving GPS receivers.

base symbol

In ArcGIS Tracking Analyst, the default symbol used to represent an event or a feature on a map.

base table

In a geodatabase, the spatially-enabled DBMS table that holds the main attribute values of a dataset. A business table with a spatial column is a feature class, and a business table with a raster column is a raster dataset or a raster catalog. In the database, the business table name is the dataset name.

base tag

A text formatting tag that allows control of how the ESRI Maplex Labeling Engine places labels based on multiple fields relative to a feature. The field identified with the base tag is placed nearest the feature, and other fields are placed relative to the position of the base field.

baseline

An accurately surveyed line from which other lines or the angles between them are measured.

basemap

A map depicting background reference information such as landforms, roads, landmarks, and political boundaries, onto which other thematic information is placed. A basemap is used for locational reference and often includes a geodetic control network as part of its structure.

batch file

A text file containing commands that is sent to the CPU to be executed automatically. A batch file allows the central processing unit (CPU) to process the commands at off-peak times or at a regularly scheduled time, rather than on demand from the user.

batch geocoding

The process of geocoding many address records at the same time.

batch mode operation

A procedure which uses a given ArcToolbox tool to process a set of information, or batch, rather than applying the tool to one piece at a time. Batch mode operation is available through tools in ArcGIS 8.3 and previous versions.

batch processing

A method for processing data automatically in which the data is grouped into batches and executed by the computer at one time, without user interaction.

batch table

In ArcToolbox, a table which displays the input name, user-selected parameters, and output name, where applicable, for all entries pertaining to a group, or batch, of jobs. Batch tables are available through tools in ArcGIS 8.3 and previous versions.

batch vectorization

An automated process that converts raster data into vector features for an entire raster or a portion of it based on user-defined settings.

bathymetric curve

A line on a map connecting points of equal depth below a hydrographic datum.

bathymetric map

A map representing the topography of a seafloor or lake bed, using contour lines to indicate depth.

bathymetry

The science of measuring and charting the depths of water bodies to determine the topography of a lake bed or seafloor.

battle dimension

In MOLE, the primary area in which a force unit operates, such as air, space, ground, sea, surface, and subsurface.

battleships grid

A grid of numbered rows and lettered columns (or vice versa) superimposed on a map, used to find and identify features. Alphanumeric grids are commonly used as a reference system on local street maps.

baud rate

In communications, the number of electrical cycles, or signals, transmitted per second. At lower transfer speeds the baud rate equals the data transfer rate measured in bps, or bits per second. Baud rate and bps are still sometimes used interchangeably, though inaccurately, since current standards allow for the encoding of multiple bits into a single cycle.

Bayes' theorem

A theorem developed by English mathematician Thomas Bayes (1702-1761) about conditional probability. It states that the probability of a given event, given the original data and some new data, is proportional to the probability of the event given the original data only, and the probability of the new data given the original data and the event.

Bayesian statistics

A statistical approach to measuring likelihood. Bayesian estimates are based on the synthesis of a prior distribution and current sample data. Classical approaches to statistics estimate the probability of an event by averaging all possible data. The Bayesian approach, in contrast, weights probability according to actual data from a particular situation. It also factors in data from sources outside the statistical investigation, such as past experience, expert opinion, or prior belief. This outside information is described by a distribution that includes all possible values for the parameter.

bearing

The horizontal direction of a point in relation to another point, expressed as an angle from a known direction, usually north, and usually measured from 0 degrees at the reference direction clockwise through 360 degrees. Bearings are often referred to as true bearings, magnetic bearings, or assumed bearings, depending on whether the meridian is true, magnetic, or assumed.

bearing method

In Survey Analyst for field measurements, one of two methods for computing the coordinate geometry traverse. The bearing method uses compass directions for the orientation of each course.

behavior

The actions or characteristics exhibited by an object in a database, as defined by a set of rule.

benchmark

A brass or bronze disk, set in a concrete base or similarly permanent structure, inscribed with a mark showing its elevation above or below an adopted vertical datum.

best available map

The most suitable data source for a map.

best route

The route of least impedance between two or more locations, taking into account connectivity and travel restrictions such as one-way streets and rush-hour traffic.

Bezier curve

A curved line whose shape is derived mathematically rather than by a series of connected vertices. In graphics programs, a Bézier curve usually has two endpoints and two handles that can be moved to change the direction and the steepness of the curve. Bézier curves are named for the French engineer Pierre Bézier (1910-1999).

Bhattacharyya distance

In digital image processing, a measure of the theoretical distance between two normal distributions of spectral classes, which acts as an upper limit on the probability of error in a Bayesian estimate of correct classification. Bhattacharyya distance is named for the Indian mathematician Anil Kumar Bhattacharyya (1915–1996).

big endian

A computer hardware architecture in which, within a multibyte numeric representation, the most significant byte has the lowest address and the remaining bytes are encoded in decreasing order of significance.

bilinear interpolation

A resampling method that uses a weighted average of the four nearest cells to determine a new cell value.

billboarding

A method for displaying graphics associated with features in a three-dimensional map display by posting them vertically as two-dimensional symbols and orienting them to always face the user.

bin

In a variogram map, each cell that groups lags with similar distance and direction. Bins are commonly formed by dividing the sample area into a grid of cells or sectors, and are used to calculate the empirical semivariogram for kriging.

binary

In computing, having only two states, such as yes or no, on or off, true or false, or 0 or 1.

binary file

A file that contains data encoded as a sequence of bits (ones and zeros) instead of plain text. A binary file, such as a DLL or an executable file, contains information that can be directly loaded or executed by a computer.

binary large object

A large block of data, such as an image, a sound file, or geometry, stored in a database. The database cannot read the BLOB's structure and only references it by its size and location.

binding

In computer programming, the process by which a program discovers an object's methods and properties.

bingo grid

A grid of numbered rows and lettered columns (or vice versa) superimposed on a map, used to find and identify features. Alphanumeric grids are commonly used as a reference system on local street maps.

binomial distribution

A distribution describing the probability of obtaining exactly K successes in N independent trials, where each trial results in either a success or a failure.

biogeography

The study of the geographical distribution of living things.

biomass

The total amount of organic matter in a defined area; usually refers to vegetation.

bit

The smallest unit of information within a computer. A bit can have one of two values, 1 and 0, that can represent on and off, yes and no, or true and false.

bit depth

The range of values that a particular raster format can store, based on the formula 2n. An 8-bit depth dataset can store 256 unique values.

bitmap

An image format in which one or more bits represent each pixel on the screen. The number of bits per pixel determines the shades of gray or number of colors that a bitmap can represent.

blind digitizing

A method of manual digitizing in which the operator has no graphic display on hand with which to see the digitized coordinates as they are captured.

BLOB

Acronym for binary large object. A large block of data, such as an image, a sound file, or geometry, stored in a database. The database cannot read the BLOB's structure and only references it by its size and location.

block

In ArcGIS, a group of records in a compressed file geodatabase feature class or table that are stored together. The arrangement of compressed data into blocks helps optimize query performance.

block attribute

In CAD, a collection of objects that can be associated to form a single object.

block group

A unit of U.S. census geography that is a combination of census blocks. A block group is the smallest unit for which the U.S. Census Bureau reports a full range of demographic statistics. There are about 700 residents per block group. A block group is a subdivision of a census tract.

block kriging

A kriging method in which the average expected value in an area around an unsampled point is generated rather than the estimated exact value of an unsampled point. Block kriging is commonly used to provide better variance estimates and smooth interpolated results.

blocking

In ArcGIS, a geocoding indexing process that reduces the number of potential matches that need to be checked.

blunder

In surveying, a defective measurement that can be detected by a statistical test.

bookmark

In ArcWeb Services, a shortcut that saves the current map view, including extents, active layers, and styles for future use.

Boolean expression

An expression, named for the English mathematician George Boole (1815-1864), that results in a true or false (logical) condition. For example, in the Boolean expression "HEIGHT > 70 AND DIAMETER = 100," all locations where the height is greater than 70 and the diameter is equal to 100 would be given a value of 1, or true, and all locations where this criteria is not met would be given a value of 0, or false.

Boolean operation

A GIS operation that uses Boolean operators to combine input datasets into a single output dataset.

Boolean operator

A logical operator used in the formulation of a Boolean expression. Common Boolean operators include AND, which specifies a combination of conditions (A and B must be true); OR, which specifies a list of alternative conditions (A or B must be true); NOT, which negates a condition (A but not B must be true); and XOR (exclusive or), which makes conditions mutually exclusive (A or B may be true but not both A and B).

border arcs

The arcs that create the boundary line of a polygon coverage.

boundary

A line separating adjacent political entities, such as countries or districts; adjacent tracts of privately-owned land, such as parcels; or adjacent geographic zones, such as ecosystems. A boundary is a line that may or may not follow physical features, such as rivers, mountains, or walls.

boundary effect

A problem created during spatial analysis, caused by arbitrary or discrete boundaries being imposed on spatial data representing nondiscrete or unbounded spatial phenomena. Boundary problems include edge effects, in which patterns of interaction or interdependency across the borders of the bounded region are ignored or distorted, and shape effects, in which the shape imposed on the bounded area affects the perceived interactions between phenomena.

boundary feature weight

One of two types of feature weights that allow control of how labels are placed relative to polygon features in ArcMap. Higher feature weights prevent labels from being placed over features. A high boundary feature weight keeps labels off of the edge of a polygon, but does not prevent the label from being placed within the boundary.

boundary line

A division between adjacent political entities, tracts of private land, or geographic zones. Boundary lines may be imaginary lines, physical features that follow those lines, or the graphical representation of those lines on a map. Boundary lines between privately owned land parcels are usually called property lines.

boundary monument

An object that marks an accurately surveyed position on or near a boundary.

boundary network

In Survey Analyst - Cadastral Editor, an irregular mesh of parcel boundaries, connection lines and control points representing a cadastral fabric. A boundary network represents parcels implicitly joined together, and is used by least-squares adjustment to distribute error from fixed control points based on the precision of boundary dimensions (bearings and distances).

boundary survey

A map that shows property lines and corner monuments of a parcel of land.

bounding rectangle

The rectangle, aligned with the coordinate axes and placed on a map display, that encompasses a geographic feature or group of features or an area of interest. It is defined by minimum and maximum coordinates in the x and y directions and is used to represent, in a general way, the location of a geographic area.

Bowditch rule

A widely used rule for adjusting a traverse that assumes the precision in angles or directions is equivalent to the precision in distances. This rule distributes the closure error over the whole traverse by changing the northings and eastings of each traverse point in proportion to the distance from the beginning of the traverse. More specifically, a correction factor is computed for each point as the sum of the distances along the traverse from the first point to the point in question, divided by the total length of the traverse. The correction factor at each point is multiplied by the overall closure error to get the amount of error correction distributed to the point's coordinates. The compass rule is also known as the Bowditch rule, named for the American mathematician and navigator Nathaniel Bowditch (1773-1838).

break

In ArcGIS Network Analyst, an object used in vehicle routing problem (VRP) analysis. A break can be used to model a specified period of rest along a route within a vehicle routing problem VRP instance.

breakline

A line in a TIN that represents a distinct interruption in the slope of a surface, such as a ridge, road, or stream. No triangle in a TIN may cross a breakline (in other words, breaklines are enforced as triangle edges). Z-values along a breakline can be constant or variable.

brightness theme

In 3D Analyst and Spatial Analyst for ArcView 3.x, a grid theme whose cell values are used to vary the brightness of another grid theme. The cell values in one grid can be visually plotted against those in another. Most commonly, hillshade grids are used as brightness themes for elevation grids. The effect is to display the elevation surface in relief.

browse graphic

An image associated with data to provide a general idea of what the service looks like. In ArcWeb Services, the browse graphic appears in the Content Library and Service Library and is defined in the metadata.

B-tree

A tree data structure used for indexing data within a database or file system implementation. In a B-tree structure, data is sorted into a set of hierarchical nodes, usually using only three or four levels. The limited number of levels makes effective searches possible, because most of the nodes in the tree do not have to be accessed during a search.

buffer

A zone around a map feature measured in units of distance or time. A buffer is useful for proximity analysis.

bug

In computing, a flaw or error in a software program or hardware component that prevents it from performing the way it should.

build

In ArcGIS, the process of creating a network system. For geometric networks, this includes establishing connectivity, creating network features, and creating logical network tables. For network datasets, this includes establishing connectivity, creating network elements, and assigning network attribute values.

build parcel

In Survey Analyst - Cadastral Editor, a cadastral fabric editing command that creates a parcel from construction lines and legal records.

Builder

A Web tool for creating and modifying content and publishing services. Users can access Builder through the ArcWeb Services Web site.

bus

A set of conductors that provide communications links between the various functional components of a computer, such as memory and peripheral devices.

business table

In a geodatabase, the spatially-enabled DBMS table that holds the main attribute values of a dataset. A business table with a spatial column is a feature class, and a business table with a raster column is a raster dataset or a raster catalog. In the database, the business table name is the dataset name.

bust

A discrepancy between existing coordinates and computed coordinates that occurs when the final point of a closed traverse has known coordinates and the final course of a traverse computes different coordinates for the same survey point.

button

A command that executes a function, macro, or custom code when clicked.

byte

The smallest addressable unit of data storage within a computer, almost always equivalent to 8 bits and containing one character.

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C

C

A common, flexible, programming language.

C/A code

The standard PRN code used by most civilian GPS receivers.

C++

An object-oriented programming language, extended from C.

C4I

In defense, an abbreviation used to signify that a computer program or system supports command, control, communication, computers, and information.

CAD

Acronym for computer-aided design. A computer-based system for the design, drafting, and display of graphical information. Also known as computer-aided drafting, such systems are most commonly used to support engineering, planning, and illustrating activities.

CAD dataset

The feature representation of a CAD file in a geodatabase-enforced schema. A CAD feature dataset is comprised of five read-only feature classes: points, polylines, polygons, multipatch and annotation. ArcGIS supported formats include DWG (AutoCAD), DXF (AutoDesk Drawing Exchange Format), and DGN (the default Microstation file format).

CAD drawing

The digital equivalent of a drawing, figure, or schematic created using a CAD system.

CAD drawing dataset

The pictorial representation of an entire CAD file that can be viewed in any ArcGIS application with a display. The CAD drawing dataset is a vector data source of a mixed feature type in which the symbology is set to mimic that of the originating CAD application. The graphic properties of a CAD drawing dataset's objects can be identified, but the dataset is not usable for feature class-based queries or analysis.

CAD feature class

A read-only member of a CAD feature dataset, comprised of one of the following: polylines, points, polygons, multipatch, or annotation. The feature attribute table of a CAD feature class is a virtual table comprised of select CAD graphic properties and any existing field attribute values.

CAD feature dataset

The feature representation of a CAD file in a geodatabase-enforced schema. A CAD feature dataset is comprised of five read-only feature classes: points, polylines, polygons, multipatch and annotation. ArcGIS supported formats include DWG (AutoCAD), DXF (AutoDesk Drawing Exchange Format), and DGN (the default Microstation file format).

CAD file

The digital equivalent of a drawing, figure, or schematic created using a CAD system. CAD files are the data source for CAD drawing datasets, feature datasets and feature classes. ArcGIS software-supported formats include DWG (AutoCAD), DXF (AutoDesk Drawing Exchange Format), and DGN (the default Microstation file format). A CAD file is represented in ArcCatalog with a CAD feature dataset and a CAD drawing dataset.

CAD layer

A layer that references a set of CAD data. CAD data is vector data of a mixed feature type. CAD layers may be of two types: CAD drawing dataset layers, in which one map layer represents the entire CAD file, and CAD feature layers, in which data is organized by geometry type.

CAD staging geodatabase

A normalized, fixed set of feature classes and data tables of a predefined schema from a collection of input CAD drawings.

cadastral fabric

In Survey Analyst - Cadastral Editor, a network of connected parcels. Parcels are represented by parcel line features, parcel point features, and parcel polygon features, referred to in aggregate as parcel features. Parcel topology in the cadastral fabric is stored explicitly through shared or common parcel point features.

cadastral fabric accuracy levels

In Survey Analyst - Cadastral Editor, a number assigned to a parcel line that determines how much the line influences the coordinates that result from a least-squares adjustment. A line with a high accuracy level will have more influence than a line with a lower accuracy level. The highest accuracy level in the cadastral fabric is 1.

cadastral fabric history

In Survey Analyst - Cadastral Editor, the record of changes to the legal and system state of the cadastral fabric.

cadastral fabric job

In Survey Analyst - Cadastral Editor, a collection of parcels that have been extracted from the cadastral fabric for editing and least-squares adjustment. Parcels in the cadastral fabric are always edited in cadastral fabric jobs.

cadastral fabric layer

In Survey Analyst - Cadastral Editor, the map representation of a cadastral fabric for which display properties may be set; a layer in ArcMap that represents the cadastral fabric.

cadastral fabric line point

In Survey Analyst - Cadastral Editor, a point that allows a parcel corner to lie on an adjacent parcel boundary line without splitting the boundary line. Line points are constrained to lie on their parcel lines.

cadastral fabric parcel line

In Survey Analyst - Cadastral Editor, a parcel line feature in the cadastral fabric that contains dimension information. Represents parcel boundaries. Parcel lines connect up to form parcel polygons and always connect two point features in the cadastral fabric.

cadastral fabric parcel line category

In Survey Analyst - Cadastral Editor, a line type that defines how a parcel line in the cadastral fabric will be managed by the cadastral fabric editor. For example, connection lines are managed differently than boundary lines.

cadastral fabric parcel point

In Survey Analyst - Cadastral Editor, a point represents a parcel corner or the end of a connection line. A parcel point always has computed x- and y-coordinates.

cadastral fabric sublayer

In Survey Analyst - Cadastral Editor, an internal feature class that forms part of the cadastral fabric. Cadastral Fabric sublayers include lines, points, polygons, line points, and control points.

cadastral fabric topology

In Survey Analyst - Cadastral Editor, the topological relationships explicit in the cadastral fabric data model.

cadastral survey

A boundary survey taken for the purposes of ownership and taxation.

cadastre

An official record of the dimensions and value of land parcels, used to record ownership and assist in calculating taxes.

calibration

The comparison of the accuracy of an instrument's measurements to a known standard.

callout line

A line on a map extending between a feature's geographic position and its corresponding symbol or label, used in areas where there is not enough room to display a symbol or label in its correct location.

camera

In ArcScene and ArcGlobe, an object that defines the perspective of a scene or globe's display.

camera station

In aerial photography, each point in the flight path at which the camera exposes the film.

candidate

A record returned as a potential match for an address in the geocoding process.

candidate key

In a relational database, any key that can be used as the primary key in a table.

capacity

In location-allocation, the maximum number of people or units that a center can service, contain, or have assigned to it.

caption

In ArcGIS, the text for a command that appears with the "Text Only" and "Image and Text" display types. As part of the user interface, captions are customizable by the user.

cardinal direction

One of the four compass directions on the earth's surface: north, south, east, or west.

cardinal point

One of the four compass directions on the earth's surface: north, south, east, or west.

cardinality

The correspondence or equivalency between sets; how sets relate to each other. For example, if one row in a table is related to three rows in another table, the cardinality is one to many.

carrier

An electromagnetic wave, such as radio, with modulations that are used as signals to transmit information.

carrier-aided tracking

Signal processing that uses the GPS carrier signal to lock onto the PRN code generated by the satellite.

carrier-phase GPS

GPS measurements that are calculated using the carrier signal of a satellite.

carrying contour

A single line representing multiple coincident contour lines, used to show vertical topographic features such as cliffs, cuts, and fills.

Cartesian coordinate system

A two-dimensional, planar coordinate system in which horizontal distance is measured along an x-axis and vertical distance is measured along a y-axis. Each point on the plane is defined by an x,y coordinate. Relative measures of distance, area, and direction are constant throughout the Cartesian coordinate plane. The Cartesian coordinate system is named for the French mathematician and philosopher René Descartes (1596-1650).

cartogram

A diagram or abstract map in which geographical areas are distorted proportionally to the value of an attribute.

cartographer

One who practices the art and science of expressing graphically, usually through maps, the natural and social features of the earth.

cartographic generalization

The abstraction, reduction, and simplification of features so that a map is clear and uncluttered at a given scale.

cartography

The art and science of expressing graphically, usually through maps, the natural and social features of the earth.

cartouche

An ornamental frame on a map, usually around the map's title. Cartouches are rarely used on modern maps.

Cascading Style Sheets

A standard for defining the layout or presentation of an HTML or XML document. Style information includes font size, background color, text alignment, and margins. Multiple style sheets may be applied to "cascade" over previous style settings, adding to or overriding them. The World Wide Web Consortium maintains the CSS standard.

CASE

Acronym for computer-aided software engineering. Any software that assists with the development and maintenance of software, especially the analysis and design. Complex tasks that often require many lines of code are simplified with CASE user interfaces and code generators.

Catalog tree

In ArcCatalog, a hierarchical view of folder connections which provide access to GIS data stored on local disks or shared on a network that allows users to manage connections to databases and GIS servers.

catchment

A basin-like terrestrial region consisting of all the land that drains water into a common terminus.

categorical raster

A raster that typically represents phenomena that have clear boundaries with attributes that are descriptions, classes, or categories. Generally, integers are used for the cell values. In a raster of land cover, for example, the value 1 might represent forestland, the value 2 urban land, and so on. It is assumed that the phenomena that each value represents fill the entire area of the cell. Rasters representing land use, political boundaries or ownership are examples of discrete rasters.

category

In ArcWeb Services, a collection of related data files, layers, data sources, or classes that show the primary use for data and help with display and navigation. Administrative, cultural, and elevation are examples of categories within ArcWeb Services.

CATID

Acronym for Component Category ID. A unique string assigned to locally related COM classes to group them together. A CATID is a type of Globally Unique IDentifier (GUID).

CBSA

A geographic region containing at least one urban area with a population of at least 10,000, defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. A core-based statistical area can be a metropolitan statistical area or a micropolitan statistical area.

CD

An optical disk, slightly less than 5 inches in diameter, used to store up to approximately 650 megabytes of data.

celestial sphere

The sky, considered as the inside of a sphere of infinitely large radius that surrounds the earth, on which all celestial bodies except the earth are imagined to be projected.

cell

The smallest unit of information in raster data, usually square in shape. In a map or GIS dataset, each cell represents a portion of the earth, such as a square meter or square mile, and usually has an attribute value associated with it, such as soil type or vegetation class.

cell selection

The process of selecting raster cells either interactively or by using a SQL query.

cell size

The dimensions on the ground of a single cell in a raster, measured in map units. Cell size is often used synonymously with pixel size.

cell statistics

An ArcGIS Spatial Analyst function that calculates a statistic for each cell of an output raster that is based on the values of each cell in the same location of multiple input rasters.

cellular automaton

A mathematical construction consisting of a row or grid of cells in which each cell has an initial value—from a known and limited number of possible values—and all cells are simultaneously evaluated and updated according to their internal states and the values of their neighbors. The simplest cellular automaton is a row in which each cell has one of two values, such as red or green. In this case, there are eight possible value combinations for a cell and its neighbors. (If a green cell with two red neighbors is notated RGR, then the eight combinations are RRR, RRG, RGR, GRR, RGG, GRG, GGR, GGG.) A set of rules determines whether or not a cell changes value when it is evaluated. A sample rule might be, "A green cell becomes red if it has a red neighbor on both sides." Successive updates, or generations, of a cellular automaton may produce complex patterns. Cellular automata are of interest in spatial modeling and are often used to model land-cover change.

census block

The smallest geographic entity for which the U.S. Census Bureau tabulates decennial census data. Many blocks correspond to city blocks bounded by streets, but blocks in rural areas may include several square miles and have some boundaries that are not streets. The Census Bureau established blocks covering the entire nation for the first time in 1990. Previous censuses dating back to 1940 had blocks established only for part of the nation.

census geography

Any one of various types of precisely defined geographic areas used by the U.S. Census Bureau to collect and aggregate data. The largest unit of area is the entire United States, while the smallest is a census block.

census tract

A small, statistical subdivision of a county that usually includes approximately 4,000 inhabitants but may include from 2,500 to 8,000 inhabitants. A census tract is designed to encompass a population with relatively uniform economic status, living conditions, and some demographic characteristics. Tract boundaries normally follow physical features but may also follow administrative boundaries or other nonphysical features. A census tract is a combination of census block groups.

center

The point in a circle or in a sphere equidistant from all other points on the object.

centerline

A line digitized along the center of a linear geographic feature, such as a street or a river, that at a large enough scale would be represented by a polygon.

centerline vectorization

The generation of vector features along the center of connected cells. It is typically used for vectorizing scanned parcel and survey maps.

centerpoint

In aerial photography, the point at the exact center of an aerial photograph.

central meridian

The line of longitude that defines the center and often the x-origin of a projected coordinate system. In planar rectangular coordinate systems of limited extent, such as state plane, grid north coincides with true north at the central meridian.

centroid

The geometric center of a feature. Of a line, it is the midpoint; of a polygon, the center of area; of a three-dimensional figure, the center of volume.

CGI

Acronym for Common Gateway Interface. A standard for scripts that run external programs from a World Wide Web server. CGI typically specifies how to pass arguments to the program via HTTP requests; defines a set of environmental variables made available to the program; and generates output, usually in HTML format, that is passed back to the browser. CGI scripts are frequently designed to access information in a database and format the results as HTML, convert information retrieved from an interactive Web page into a database, send datasets, and so on.

chain

A unit of length equal to 66 feet, used especially in U.S. public land surveys. Ten square chains equal 1 acre.

chain code

A method of drawing a polygon as a series of straight line segments defined as a set of directional codes, with each code following the last like links in a chain.

change detection

A process that measures how the attributes of a particular area have changed between two or more time periods. Change detection often involves comparing aerial photographs or satellite imagery of the area taken at different times. The process is most frequently associated with environmental monitoring, natural resource management, or measuring urban development.

character

A letter, digit, or special graphic symbol treated as a single unit of data and usually stored as one byte.

chart

A map used to plot a course for air or water navigation.

check-in

In disconnected editing, the procedure that transfers a copy of data into a master geodatabase, overwriting the original copy of that data and reenabling it so it can be accessed and saved from that location. In checkout/check-in replication, check-in is the procedure that synchronizes the data in the parent replica with that in the child replica.

checkout

A procedure in disconnected editing that records the duplication of data from one geodatabase to another and disables the original data so that both versions cannot be accessed or saved at the same time.

checkout geodatabase

In ArcGIS versions 8.3–9.1, a personal or ArcSDE geodatabase that contains data checked out from a master geodatabase during disconnected editing.

checkout version

The data version created in a checkout geodatabase when data is checked out to that database during disconnected editing. The checkout version is created as a copy of the synchronization version. Only the edits made to this checkout version can be checked back in to the master geodatabase.

checkout/check-in replication

A type of geodatabase replication that involves copying data to a destination geodatabase, editing that data in the destination, and then merging the changes with the source geodatabase. In ArcGIS and ArcSDE, the destination can be a file, personal, or ArcSDE geodatabase, while the source must be an ArcSDE geodatabase. Once the data is merged (synchronized), checkout/check-in replication is completed.

child replica

In geodatabase editing, data that has been copied to a destination geodatabase during the replication process.

chi-square statistic

A statistic used to assess how well a model fits the data. It compares categorized data with a multinomial model that predicts the relative frequency of outcomes in each category to see to what extent they agree.

chord

A straight line that joins two points on a curve.

choropleth map

A thematic map in which areas are distinctly colored or shaded to represent classed values of a particular phenomenon.

chroma

The saturation, purity, or intensity of a color.

chronometer

An extremely accurate clock that remains accurate through all conditions of temperature and pressure. The chronometer was developed in the eighteenth century for determining longitude at sea, but its scientific and navigational use has been made obsolete by the invention of quartz and atomic clocks.

CHUM

Acronym for Chart Updating Manual. A document containing updates to aeronautical information, used by the U.S. military to update their current published products with the latest information.

circle

A two-dimensional geometric shape for which the distance from the center to any point on the edge is equal; the closed curve defining such a shape.

circular arc

A curved line that is a section of a circle, with two vertices, one situated at each endpoint.

circular variance

A measure of directional variation, on a scale from zero to one, among a set of line vectors. Circular variance approaches zero when all vectors point in roughly the same direction and approaches one when the vectors point in markedly different directions.

civilian code

The standard PRN code used by most civilian GPS receivers.

Clarke Belt

An orbit 22,245 miles (35,800 kilometers) above the equator in which a satellite travels at the same speed that the earth rotates. The Clarke Belt was named after the writer and scientist Arthur C. Clarke. It is also referred to as a geostationary orbit.

Clarke ellipsoid of 1866

A reference ellipsoid having a semimajor axis of approximately 6,378,206.4 meters and a flattening of 1/294.9786982. It is the basis for the North American Datum of 1927 (NAD27) and other datums. The Clarke ellipsoid of 1866 is also known as the Clarke spheroid of 1866.

Clarke spheroid of 1866

A reference ellipsoid having a semimajor axis of approximately 6,378,206.4 meters and a flattening of 1/294.9786982. It is the basis for the North American Datum of 1927 (NAD27) and other datums. The Clarke ellipsoid of 1866 is also known as the Clarke spheroid of 1866.

class

A set of entities grouped together on the basis of shared attribute values.

class identifier

A COM term referring to the globally unique number that is used by the system registry and the COM framework to identify a particular coclass.

class intervals

A set of categories for classification that divide the range of all values so that each piece of data is contained within a nonoverlapping category.

classification

The process of sorting or arranging entities into groups or categories; on a map, the process of representing members of a group by the same symbol, usually defined in a legend.

classification table

An ASCII file in the geocoding rule base that identifies and classifies keywords that may appear in an address, such as street types and directions. Classification tables have a .cls file extension.

CLDC

Acronym for Connected Limited Device Configuration. A framework for developing J2ME applications for devices with very limited resources, such as wireless devices.

clean data

Data that is free from error.

cleaning

Improving the appearance of scanned or digitized data by correcting overshoots and undershoots, closing polygons, performing coordinate editing, and so on.

clearinghouse

A repository structure, physical or virtual, that collects, stores, and disseminates information, metadata, and data. A clearinghouse provides widespread access to information and is generally thought of as reaching or existing outside organizational boundaries.

client

An application, computer, or device in a client/server model that makes requests to a server.

client sample

A set of live and downloadable code samples designed to show users how to access an ArcWeb service. The live samples allow users to interact with an ArcWeb service using a browser. The downloadable code samples are available in several programming languages.

client/server architecture

A software system with a central processor (server) that accepts requests from one or more user applications, computers, or devices (clients). Although client/server architecture can exist on one computer, it is more relevant to (and is typically thought of as relating to) network systems that distribute applications over computers in different locations.

client-side address locator

An address locator that is created and used on the same computer.

clinometric map

A map that represents slope with colors or shading.

clip

A command that extracts features from one feature class that reside entirely within a boundary defined by features in another feature class.

cloning

In object-oriented programming, the process of creating a new instance of a class with the same state as an existing instance.

close coupling

A high or complex degree of interconnections between the components within a program or between programs, that requires substantial overlap between methods, ontologies, class definitions, and so on.

closed loop traverse

In surveying, a traverse that starts and ends with the same survey point.

closest facility analysis

In ArcGIS Network Analyst, a type of network analysis for finding the closest locations (facilities) from sites (incidents), based on the impedance chosen—for example, finding hospitals near a car accident. When finding closest facilities, users can specify how many to find and whether the direction of travel is toward or away from the site (incident). Users can also specify a cutoff threshold beyond which ArcGIS Network Analyst will not search for a facility—for example, finding hospitals within 6 miles of a car accident.

closure error

A discrepancy between existing coordinates and computed coordinates that occurs when the final point of a closed traverse has known coordinates and the final course of a traverse computes different coordinates for the same survey point.

closure report

The summary of the difference between the endpoint coordinate of a traverse and the calculated endpoint.

CLR

Acronym for common language runtime. The execution engine for .NET Framework applications, providing services such as code loading and execution and memory management.

CLSID

Acronym for class identifier. A COM term referring to the globally unique number that is used by the system registry and the COM framework to identify a particular coclass.

cluster analysis

A statistical classification technique for dividing a population into relatively homogeneous groups. The similarities between members belonging to a class, or cluster, are high; while similarities between members belonging to different clusters are low. Cluster analysis is frequently used in market analysis for consumer segmentation and locating customers, but it is also applied to other fields.

cluster tolerance

The minimum tolerated distance between vertices in a topology. Vertices that fall within the set cluster tolerance are snapped together during the topology validation process.

clustering

A part of the topology validation process in which vertices that fall within a specified distance (cluster tolerance) of each other are snapped together.

CMYK

A color model that combines the printing inks cyan, magenta, yellow, and black to create a range of colors. Most commercial printing uses this color model.

CNT

A component of the PLTS knowledge base that contains SQL statements and custom code for feature validation extended beyond standard geodatabase domains. PLTS utilizes condition tables for enhanced validation during both database production and quality control.

Coarse/Acquisition code

The standard PRN code used by most civilian GPS receivers.

coclass

A template for an object that can be instantiated in memory.

coded value domain

A type of attribute domain that defines a set of permissible values for an attribute in a geodatabase. A coded value domain consists of a code and its equivalent value. For example, for a road feature class, the numbers 1, 2, and 3 might correspond to three types of road surface: gravel, asphalt, and concrete. Codes are stored in a geodatabase, and corresponding values appear in an attribute table.

code-phase GPS

GPS measurements calculated using the PRN code transmitted by a GPS satellite.

cognitive map

A person's perception of a place. A mental map may include the physical characteristics of a place, such as boundaries of a neighborhood, or the attributes of a place, such as a neighborhood's perceived unsafe areas. A mental map is primarily a psychological construct, although it may also be rendered as an actual map.

COGO

Acronym for coordinate geometry. A method for calculating coordinate points from surveyed bearings, distances, and angles.

COGO composite measurement

In Survey Analyst for field measurements, measurements that comprise a set of interdependent COGO simple measurements.

COGO simple measurement

In Survey Analyst for field measurements, measurements that model values that define vectors, directions, lengths, and orthogonal offsets.

coincident

Occupying the same space. Coincident features or parts of features occupy the same space in the same plane.

coincident geometry

In a geodatabase, how the coordinates of coincident features are stored. For example, if two lines are coincident, they will both be drawn in ArcMap, with one line lying precisely on top of the other. For two adjacent polygons, the coordinates for the shared boundary will be stored with each polygon and the boundary will be drawn twice.

cokriging

A form of kriging in which the distribution of a second, highly correlated variable (covariate) is used along with the primary variable to provide interpolation estimates. Cokriging can improve estimates if the primary variable is difficult, impossible, or expensive to measure, and the second variable is sampled more intensely than the primary variable.

ColdFusion

A Macromedia software product that integrates databases and Web pages using a server and development tools. ColdFusion Web pages include elements written in ColdFusion Markup Language that simplify integration with databases.

ColdFusion Connector

An ArcIMS Application Server Connector. In this environment, a request that includes ColdFusion tags is first executed on the ColdFusion Server. The ArcIMS custom ColdFusion tags are then passed to the ArcIMS Application Server for processing.

color composite

A color image made by assigning red, green, and blue colors to each of the separate monochrome bands of a multispectral image and then superimposing them.

color map

A set of values that are associated with specific colors. Color maps are most commonly used to display a raster dataset consistently on many different platforms.

color model

Any system that organizes colors according to their properties for printing or display. Examples include RGB (red, green, blue), CMYK (cyan, magenta, yellow, black), HSB (hue, saturation, brightness), HSV (hue, saturation, value), HLS (hue, lightness, saturation), and CIE-L*a*b (Commission Internationale de l'Eclairage-luminance, a, b).

Color Palette

In ArcWeb Services, a tool for selecting colors and transparency. The Color Palette lets a user select an object's fill and outline color by choosing from a color spectrum or by defining colors numerically. A user can also define the transparency of the color for an object.

color ramp

A range of colors used to show ranking or order among classes on a map.

color separation

In printing, the use of a separate printing plate for each ink color used.

column

An item in an attribute table.

COM

Acronym for Component Object Model. A binary standard that enables software components to interoperate in a networked environment regardless of the language in which they were developed. Developed by Microsoft, COM technology provides the underlying services of interface negotiation, life-cycle management (determining when an object can be removed from a system), licensing, and event handling. The ArcGIS system is created using COM objects.

COM contract

The COM requirement that interfaces, once published, cannot be altered.

COM interface

A grouping of logically related virtual functions, implemented by a server object, allowing a client to interact with the server object. Interfaces form the basis of COM’s communication between objects and the basis of the COM contract.

combinatorial operator

A kind of mathematical operator that interprets input with Boolean values. Combinatorial operators assign a different number to each unique combination of input values.

combo box

A user interface tool that combines the features of a text box and a drop-down list. For example, the Location combo box in ArcCatalog allows the selection of an item in the Catalog tree by typing its path or choosing its path from a drop-down list.

command

An instruction to a computer program, usually one word or concatenated words or letters, given by the user from a control device, such as a keyboard, or read from a file by a command interpreter.

command bar

A toolbar, menu bar, menu, or shortcut menu in an ArcGIS application.

command line

A string of text that acts as a command, typed at an interface prompt.

command line interface

A format of the input and output of a program in which the user enters commands by means of strings of text typed on a keyboard, as opposed to selecting commands from graphical prompts such as icons or dialog boxes.

Command Line Window

In geoprocessing, a window that provides a command line for running tools and a message window for viewing the status messages created when running those tools.

command prompt window

A window accessible from the Windows Start menu in which MS-DOS commands are typed.

comment

In Survey Analyst for field measurements, a field that provides additional information about the computation.

commercial off-the-shelf

Commercially available software or systems that are ready to use and which do not require significant customization.

committed read

The isolation level in a database management system (DBMS) in which transactions read committed data only — they don't read data that has not been committed.

Common Gateway Interface

A standard for scripts that run external programs from a World Wide Web server. CGI typically specifies how to pass arguments to the program via HTTP requests; defines a set of environmental variables made available to the program; and generates output, usually in HTML format, that is passed back to the browser. CGI scripts are frequently designed to access information in a database and format the results as HTML, convert information retrieved from an interactive Web page into a database, send datasets, and so on.

common language runtime

The execution engine for .NET Framework applications, providing services such as code loading and execution and memory management.

compact disc

An optical disk, slightly less than 5 inches in diameter, used to store up to approximately 650 megabytes of data.

compaction

A process that rearranges and consolidates the data in a file so that it occupies a single, contiguous space, allowing the data in each file to be accessed more efficiently.

comparison threshold

The degree of uncertainty that can be tolerated in the spelling of a keyword used in a search, including phonetic errors and the random insertion, deletion, replacement, or transposition of characters.

compass

An instrument used to find the direction of north from one's current location, consisting of a case with compass points marked around its edge and a floating magnetic needle that pivots to point to magnetic north.

compass north

The direction from a point on the earth's surface following a great circle toward the magnetic north pole, indicated by the north-seeking end of a compass.

compass point

An indication of direction. One of the 32 divisions into which the circle around the needle of a compass is divided, each equal to 11.25 degrees.

compass rose

A diagram of compass points drawn on a map or chart, subdivided clockwise from 0 to 360 degrees with 0 indicating true north. On older maps and charts a compass rose was a decorated diagram of cardinal points, divided into 16 or 32 points.

compass rule

A widely used rule for adjusting a traverse that assumes the precision in angles or directions is equivalent to the precision in distances. This rule distributes the closure error over the whole traverse by changing the northings and eastings of each traverse point in proportion to the distance from the beginning of the traverse. More specifically, a correction factor is computed for each point as the sum of the distances along the traverse from the first point to the point in question, divided by the total length of the traverse. The correction factor at each point is multiplied by the overall closure error to get the amount of error correction distributed to the point's coordinates. The compass rule is also known as the Bowditch rule, named for the American mathematician and navigator Nathaniel Bowditch (1773-1838).

compiler

A program used in software development that translates the lines of a programmer's code from one programming language to another, usually from a high-level language to the ones and zeros of machine language.

complex dynamic event

In ArcGIS Tracking Analyst, a type of complex temporal event that includes two components and involves a moving object, such as an airplane. The moving object's geographical location changes through time, so its additional attributes are stored in an input table.

complex edge feature

In a geodatabase, a linear network feature that corresponds to one or more network elements in the logical network.

complex junction feature

In ArcGIS 8.3 and previous versions, a junction feature in a geodatabase that corresponds to more than one network element in the logical network. For example, the state of the junction determines whether features can be connected or disconnected. This is not a concept that can be modeled in ArcGIS 9.0 and later versions.

complex market area

An area calculated by finding the outermost customers of a store along several vectors and connecting them. Complex market areas are more accurate than simple market areas because they respond to physical and cultural barriers. They are sometimes called amoebas because of their irregular shapes.

complex stationary event

A type of complex temporal event in ArcGIS Tracking Analyst that includes two components and involves a stationary object, such as a traffic sensor. The sensor's geographical location will not change, so its location information is stored in the input feature class.

complex temporal event

An event in ArcGIS Tracking Analyst that contains two components: one with persistent object information, and one with observations of the object through time. The merger of the temporal observations with the temporal object creates a complex event record or message. There are two types of complex temporal events: dynamic and stationary.

component

In COM, a binary unit of code that can be used to create COM objects.

component category

A section of the registry that can be used to categorize classes by their functionality. Component categories are used extensively in ArcGIS to allow extensibility of the system.

Component Category Manager

An ArcGIS utility program (Categories.exe) that can be used to view and manipulate component category information.

Component Object Model

A binary standard that enables software components to interoperate in a networked environment regardless of the language in which they were developed. Developed by Microsoft, COM technology provides the underlying services of interface negotiation, life-cycle management (determining when an object can be removed from a system), licensing, and event handling. The ArcGIS system is created using COM objects.

composite measurement

In Survey Analyst for field measurement, a set of simple measurements that are related and applied as a group.

composite relationship

A link or association between objects where the lifetime of one object controls the lifetime of its related objects. For example, the association between a highway and its shield markers is a composite relationship, since the shield markers should not exist without the highway.

composition

A UML term used to describe a form of association in which the lifetime of the whole controls the lifetime of the parts. In a composition, the instances of two classes depend on each other. The whole controls the location and lifetime of its parts. For example, in ArcMap, a map is composed of layers. If you move a map on a layout, the layers move, and if you delete the map, its layers get deleted; therefore, the lifetime of these objects depend on one another.

compound element

Within metadata, a group of data elements (including other compound elements) that together describe a characteristic of a spatial dataset in more detail than can be described by an individual data element.

compound key

A primary key that requires two or more fields to be unique.

compression

The process of reducing the size of a file or database. Compression improves data handling, storage, and database performance. Examples of compression methods include quadtrees, run-length encoding, and wavelets.

compromise projection

A projection that does not have equal area, conformal, or equidistant characteristics. The compromise projection is an attempt at balance between these characteristics, and is often used in thematic mapping.

computation

In Survey Analyst for field measurements, a process that requires a set of input parameters to apply a set of rules, and an algorithm to calculate output parameters. The input parameters are typically coordinates and measurements. The output parameters are usually coordinates.

computation name

In Survey Analyst for field measurements, a unique identifier that calls or retrieves a specific type of computation, defined on the General tab of the Survey Explorer.

computation network

In Survey Analyst for field measurements, a sequence of computation dependencies—the output points of some computations are used as the input for one or more others.

Computation Network Analysis window

In Survey Analyst for field measurements, a window that displays information about the computation network, such as breaks in the sequence, computation states, and computation network cycles.

computation network cycles

In Survey Analyst for field measurements, a problem that occurs when a point's coordinates are used as both input and output within the same computation network. Cycles must be fixed before the whole network can be validated and brought to a state in which all computations are valid.

computation state

In Survey Analyst for field measurements, the condition of a computation. A computation may be in four different states: valid, out-of-date, incorrect, or incomplete.

Computation tool

In Survey Analyst for field measurements, a tool that interacts with the map to add measurement values to computation pages.

computational geometry

A branch of mathematics that uses algorithms to solve geometry problems. Computational geometry is used in many GIS operations, including proximity analysis, feature generalization, and automated text placement.

computer-aided design

A computer-based system for the design, drafting, and display of graphical information. Also known as computer-aided drafting, such systems are most commonly used to support engineering, planning, and illustrating activities.

computer-aided software engineering

Any software that assists with the development and maintenance of software, especially the analysis and design. Complex tasks that often require many lines of code are simplified with CASE user interfaces and code generators.

computer-assisted learning

Instruction or training that uses computer-based media instead of hard-copy materials. Computer-assisted learning is generally designed to use the strengths of computer-based media such as the ability to navigate in a nonlinear fashion through the use of hyperlinks.

concatenate

To join two or more character strings together, end to end; for example, to combine the two strings "spatial" and "analysis" into the single string "spatial analysis."

concatenate events

In linear referencing, a command that combines event records in tables containing events on the same route with the same value for specified fields. Only events in situations where the to-measure of one event matches the from-measure of the next event are combined. The concatenate events command is available for line event tables only.

concatenated key

In a relational database table, a primary key made by combining two or more keys that together form a unique identifier.

concentric rings

A method of defining the rings in an analysis so that the values inside the rings are cumulative. For example, if you had an analysis with three concentric rings and 10 households in each, the total number of households for ring 1 would be 10, the total for ring 2 would be 20 (ring 1 + ring 2), and the total for ring 3 would be 30 (ring 1 + ring 2 + ring 3).

concurrency

The ability of a DBMS to support simultaneous access by more than one user.

concurrency management

A database management process for maintaining the consistency of data while supporting simultaneous editing by more than one user. A typical technique involves locking portions of the database to prevent data corruption caused by multiple users simultaneously editing data.

concurrent use

Floating software products that are administered by a license manager. A central license manager (installed anywhere on a network) allows users to install the floating products on any number of machines. The number of seats or licenses purchased determines the number of users who can run the applications simultaneously.

condition table

A component of the PLTS knowledge base that contains SQL statements and custom code for feature validation extended beyond standard geodatabase domains. PLTS utilizes condition tables for enhanced validation during both database production and quality control.

conditional operator

A symbol or keyword that specifies the relationship between two values and is used to construct queries to a database. Examples include = (equal to), < (less than), and > (greater than).

conditional statement

A programming language statement that executes one option if the statement is true, and another if it is false. The if-then-else statement is an example of a conditional statement.

confidence level

In a statistical test, the risk, expressed as a percentage, that the null hypothesis will be incorrectly rejected because of sampling error when the null hypothesis is true. For example, a confidence level of 95 percent means that if the same test were performed 100 times on 100 different samples, the null hypothesis would be incorrectly rejected five times.

configuration file

In ArcIMS, the file that contains the core site information. ArcIMS configuration files contain all the basic information about the content to be delivered, such as location of the data and layer symbology. Typically, a configuration file contains data that defines map content and has a file extension of .axl, but it can also be used to deliver metadata or route data (as .axl files) and to serve maps created in ArcMap (.mxd or .pmf files). Regardless of their type, configuration files contain content that the service registers to the ArcIMS spatial server and Web server for processing.

configuration keyword

In ArcSDE, a name for a group of parameters that defines how geodatabase objects are stored.

conflation

A set of procedures that aligns the features of two geographic data layers and then transfers the attributes of one to the other.

conflict

In database editing, a state of incompatibility that occurs when multiple users simultaneously edit a version or reconcile two versions. Conflicts occur when the same feature or topologically related features are edited in two versions, and it is unclear which representation of the database is valid.

conflict resolution

The process of solving uncertainty within a database that occurs when two versions of the same data are edited at the same time. Conflicts can occur when multiple users simultaneously edit the same feature or topologically related features, or reconcile two versions of a dataset. Resolving a conflict requires that the user make a decision about the feature's correct representation and identify it in the Conflict Resolution dialog box.

conformal projection

A projection that preserves the correct shapes of small areas. In a conformal projection, graticule lines intersect at 90-degree angles, and at any point on the map the scale is the same in all directions. A conformal projection maintains all angles at each point, including those between the intersections of arcs; therefore, the size of areas enclosed by many arcs may be greatly distorted. No map projection can preserve the shapes of larger regions.

conformality

The characteristic of a map projection that preserves the shape of any small geographic area.

congressional district

A geographical and political division in which voters elect representatives to the U.S. House of Representatives. Each state establishes its congressional districts based on population counts, with the goal of having districts as equal in population as possible.

conic projection

A projection that transforms points from a spheroid or sphere onto a tangent or secant cone that is wrapped around the globe in the manner of a party hat. The cone is then sliced from the apex (top) to the bottom, and flattened into a plane.

conjoint boundary

A boundary common to two features. For example, in a parcel database, adjacent parcels share a boundary. Another example is a parcel that shares a boundary on one side with a river. The segment of the river that coincides with the parcel boundary shares the same coordinates as the parcel boundary.

connection

In ArcCatalog, a mechanism used to access remote file systems and shared databases.

connection line

A cadastral fabric line with bearing and distance data attached to it, commonly used to tie parcels across roads, tie in control points, or tie the point of survey commencement to the point of beginning for a particular parcel. Connection lines do not necessarily indicate parcel boundaries.

connectivity

The way in which features in GIS data are attached to one another functionally or spatially.

connectivity analysis

Any method of solving network problems such as traversability, rate of flow, or capacity, using network connectivity.

connectivity group

In network datasets, a logical grouping of point features, line features, or both, that controls how network elements are connected. Connectivity groups are defined when a network dataset is built. A network dataset may have multiple connectivity groups.

connectivity policy

In a network dataset, a property of network sources that defines how network elements connect to each other within a connectivity group. There are two types of edge-edge connectivity policies (end-point connectivity and any-vertex connectivity) and two types of edge-junction connectivity policies (honor and override).

connectivity rule

In geometric networks, a rule that constrains the type and number of network features that can be connected to one another. There are two types of connectivity rules: edge-edge and edge-junction.

connector

A visual representation of the relationship between elements in a model. Connectors join elements together to create processes. Typical processes connect an input data element, a tool element, and a derived data element.

constant azimuth

A complex curve on the earth's surface that crosses every meridian at the same oblique angle. A rhumb line path follows a single compass bearing; it is a straight line on a Mercator projection, or a logarithmic spiral on a polar projection. A rhumb line is not the shortest distance between two points on a sphere.

constrained adjustment

In Survey Analyst for field measurements, one of two phases involved when performing a least squares adjustment for a measurement network. In this phase, the emphasis is on testing the reference points as well as computing final coordinates.

constraints

Limits imposed on a model to maintain data integrity. For example, in a water network model, an 8-inch pipe cannot connect to a 4-inch pipe.

construct features

In ArcMap, an edit command that takes selected features from one or more feature classes and creates new features in a target feature class. The Construct Features tool uses the input geometries of the selected features to construct polygons or lines following polygon boundaries, depending on the geometry of the target feature class.

construction line

In Survey Analyst - Cadastral Editor, a line with a bearing and distance that is used to create geometry for a new cadastral fabric parcel.

container account

The operating system account that server object container processes run as, which is specified by the GIS server postinstallation utility. Objects running in a server container process have the same access rights to system resources as the container account.

container process

A process in which one or more server objects are running. Container processes run on SOC machines, and are started and shut down by the SOM. They are visible in the Windows Task Manager as ArcSOC.exe.

containment

A spatial relationship in which a point, line, or polygon feature or set of features is enclosed completely within a polygon.

content

In ArcWeb Services, data that may include data files, layers, or services.

Content Finder Web Service

A SOAP ArcWeb service that allows users to search the metadata information for available content in the ArcWeb system.

Content Library

A Web-based tool for viewing and maintaining information about data files, layers, and services used in ArcWeb Services. Users can access Content Library through the ArcWeb Services Web site.

Content Standard for Digital Geospatial Metadata

A publication authored by the FGDC that specifies the information content of metadata for digital geospatial datasets. The purpose of the standard is to provide a common set of terminology and definitions for concepts related to the metadata. All U.S. government agencies (federal, state, and local) that receive federal funds to create metadata must follow this standard.

conterminous

Having the same or coincident boundaries.

context menu

A list menu that pops up when the right mouse button is clicked in Windows applications. Some keyboards also have an application key that opens shortcut menus.

contiguity

In a coverage, the topological identification of adjacent polygons by recording the left and right polygon for each arc.

contiguous

Of polygons: adjacent; having a common boundary; sharing an edge.

continuous data

Data such as elevation or temperature that varies without discrete steps. Since computers store data discretely, continuous data is usually represented by TINs, rasters, or contour lines, so that any location has either a specified value or one that can be derived.

continuous feature

A feature that is not spatially discrete. The transition between possible values on a continuous surface is without abrupt or well-defined breaks.

continuous raster

A raster in which cell values vary continuously to form a surface. In a continuous raster, the phenomena represented have no clear boundaries. Values exist on a scale relative to each other. It is assumed that the value assigned to each cell is what is found at the center of the cell. Rasters representing elevation, precipitation, chemical concentrations, suitability models, or distance from a road are examples of continuous rasters.

continuous tone image

A photograph that has not been screened and so displays all the varying tones from dark to light.

contour interval

The difference in elevation between adjacent contour lines.

contour line

A line on a map that connects points of equal elevation based on a vertical datum, usually sea level.

contour tagging

Assigning elevation values to contour lines.

contrast

In remote sensing and photogrammetry, the ratio between the energy emitted or reflected by an object and that emitted or reflected by its immediate surroundings.

contrast ratio

The ratio between the maximum and minimum brightness values in an image.

contrast stretch

Increasing the contrast in an image by expanding its grayscale range to the range of the display device.

control

A basic element of a software application's GUI. Examples of controls include menus, buttons, tools, check boxes, slider bars, text input boxes, and combo boxes.

control point

An accurately surveyed coordinate location for a physical feature that can be identified on the ground. Control points are used in least-squares adjustments as the basis for improving the spatial accuracy of all other points to which they are connected.

conventional alternative hypothesis

In statistical testing, a set of assumptions that will be accepted by test data if the null hypothesis is rejected. In surveying, the alternative hypothesis assumes that there is an outlier present in a single measurement in a measurement network. The test associated with this hypothesis is the W-test.

convergence angle

The angle between a vertical line (grid north) and true north on a map.

conversion

The process of changing input data from one representation or format to another, such as from raster to vector, or from one file format to another, such as from x,y coordinate table to point shapefile.

convex hull

The smallest convex polygon that encloses a group of objects, such as points. In ArcGIS, TIN boundaries are convex hulls by default.

convex polygon

A polygon in which a straight line drawn between any two points inside the polygon is completely contained within the polygon. Visually, the boundary of a convex polygon is the shape a rubber band would take around a group of objects.

cookie cutter

A command that extracts features from one feature class that reside entirely within a boundary defined by features in another feature class.

coordinate geometry

A method for calculating coordinate points from surveyed bearings, distances, and angles.

coordinate geometry traverse

In Survey Analyst, a process of computing a sequence of survey point locations starting from an initial known point. Each new survey point is defined by a traverse course and is used as the takeoff point for the next point in the sequence. A traverse course can be defined using various combinations of directions, distances, angles, and circular arc parameters. The coordinate geometry traverse is primarily used to define coordinates based on values taken from subdivision plans.

coordinate system

A reference framework consisting of a set of points, lines, and/or surfaces, and a set of rules, used to define the positions of points in space in either two or three dimensions. The Cartesian coordinate system and the geographic coordinate system used on the earth's surface are common examples of coordinate systems.

coordinate transformation

The process of converting the coordinates in a map or image from one coordinate system to another, typically through rotation and scaling.

coordinated universal time

The official timekeeping system of the world's nations since 1972. It refers local time throughout the world to time at the prime meridian, and is based on atomic clocks, but is periodically artificially adjusted so as to always remain within 0.9 seconds of universal time. The adjustment is made by the addition of leap seconds to the course of atomic time. Coordinated universal time is abbreviated "UTC." (The abbreviation UTC does not represent the word order of "coordinated universal time" in either English or French. It is an extension of the "UT*" pattern established for versions of universal time.)

coordinates

A set of values represented by the letters xy, and optionally z or m (measure), that define a position within a spatial reference. Coordinates are used to represent locations in space relative to other locations.

core-based statistical area

A geographic region containing at least one urban area with a population of at least 10,000, defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. A core-based statistical area can be a metropolitan statistical area or a micropolitan statistical area.

correlation

An association between data or variables that change or occur together. For example, a positive correlation exists between housing costs and distance from the beach; generally, the closer a home is to the beach, the more it costs. Correlation does not imply causation. For example, there is a statistical correlation between ice cream sales and crime rates, but neither causes the other. The correlation coefficient is an index number between -1 and 1 indicating the strength of the association between two variables.

corridor

A buffer drawn around a line.

corridor analysis

A form of spatial analysis usually applied to environmental and land-use data in order to find the best locations for building roads, pipelines, and other linear transportation features.

cost

A function of time, distance, or any other factor that incurs difficulty or an outlay of resources.

cost grid

A raster dataset that identifies the cost of traveling through each cell in the raster. A cost raster can be used to calculate the cumulative cost of traveling from every cell in the raster to a source or a set of sources.

cost raster

A raster dataset that identifies the cost of traveling through each cell in the raster. A cost raster can be used to calculate the cumulative cost of traveling from every cell in the raster to a source or a set of sources.

cost-benefit analysis

An appraisal that attempts to compare the benefits (including social benefits) expected from a project with the costs (sometimes including social costs) incurred by the project over its lifetime. Generally cost-benefit analyses are used to compare alternative proposals, or to make a case for the implementation of a particular plan or system.

cost-distance analysis

The calculation of the least cumulative cost from each cell to specified source locations over a cost raster.

cost-weighted allocation

An ArcGIS Spatial Analyst function that identifies the nearest source from each cell in a cost-weighted distance grid. Each cell is assigned to its nearest source cell, in terms of accumulated travel cost.

cost-weighted direction

An ArcGIS Spatial Analyst function that provides a road map from the cost weighted distance grid, identifying the route to take from any cell, along the least-cost path, back to the nearest source.

cost-weighted distance

An ArcGIS Spatial Analyst function that uses a cost grid to assign a value—the least accumulative cost of getting back to the source—to each cell of an output grid.

COTS

Acronym for commercial off-the-shelf. Commercially available software or systems that are ready to use and which do not require significant customization.

county

The primary legal subdivision of all U.S. states except Alaska and Louisiana. The U.S. Census Bureau uses counties or equivalent entities (boroughs in Alaska, parishes in Louisiana, the District of Columbia in its entirety, and municipios in Puerto Rico) as statistical subdivisions.

county subdivision

A statistical division of a county recognized by the U.S. Census Bureau for data presentation. County subdivisions can include census county divisions, census subareas, minor civil divisions, and unorganized territories.

covariance

A statistical measure of the linear relationship between two variables. Covariance measures the degree to which two variables move together relative to their individual mean returns.

coverage

A data model for storing geographic features. A coverage stores a set of thematically associated data considered to be a unit. It usually represents a single layer, such as soils, streams, roads, or land use. In a coverage, features are stored as both primary features (points, arcs, polygons) and secondary features (tics, links, annotation). Feature attributes are described and stored independently in feature attribute tables. Coverages cannot be edited in ArcGIS 8.3 and subsequent versions.

coverage feature class

In ArcInfo, a classification describing the format of geographic features and supporting data in a coverage. Feature classes include point, arc, node, route, route system, section, polygon, and region. One or more coverage features are used to model geographic features; for example, arcs and nodes can be used to model linear features, such as street centerlines. The tic, annotation, link, and boundary feature classes provide supporting data for coverage data management and viewing.

coverage units

The units of the coordinate system in which a coverage is stored (for example, feet, meters, inches).

cracking

In ArcGIS, a part of the topology validation process in which vertices are created at the intersection of feature edges.

Crandall rule

A special-case, least-squares-based method for adjusting the closure error in a traverse. The Crandall rule is most frequently used in a closed traverse that represents a parcel from a subdivision plan to ensure that tangency between courses remains intact as, for example, when applied to a tangent curve. It assumes that course directions and angles have no error and, therefore, all error corrections are applied only to the distances. This method uses a least-squares adjustment to distribute the closure error, and applies infinite weight to the angles or direction measurements to ensure that they are not adjusted. In some circumstances the results of this adjustment method may be unexpected, or the adjustment may not be possible, and an alternative method is required. The Crandall rule was developed by C.L. Crandall around 1901.

creation date

In Survey Analyst for field measurements, an attribute of the computation that records the date of origin.

creation time

The time it takes to initialize an instance of a server object when server objects are created in the GIS server either as a result of the server starting or in response to a request for a server object by a client.

credit

A charge to access an ArcWeb service. Users use credits each time they request an ArcWeb service to perform a task, such as find a route.

critical value

The specific cutoff point that determines acceptance or rejection of a hypothesis. Critical values are determined by the choice of a level of significance (α).

crop guide

Marks that indicate the edge of the page of a finished, printed map. Cropmarks are used as a reference for trimming excess paper after printing.

crop marks

Marks that indicate the edge of the page of a finished, printed map. Cropmarks are used as a reference for trimming excess paper after printing.

cross correlation

Statistical correlation between spatial random variables of different types, attributes, names, and so on, where the correlation depends on the distance or direction that separates the locations.

cross covariance

The statistical tendency of variables of different types, attributes, names, and so on, to vary in ways that are related to each other. Positive cross covariance occurs when both variables tend to be above their respective means together, and negative cross covariance occurs if one variable tends to be above its mean when the other variable is below its mean.

cross tabulation

In a GIS, comparing attributes in different coverages or map layers according to location.

cross validation

A procedure for testing the quality of a predicted data distribution. In cross validation, a piece of data whose value is known independently is removed from the dataset and the rest of the data is used to predict its value. Full cross validation is done by removing, in turn, each piece of data from the dataset and using the rest of the data to predict its value.

cross variogram

A function of the distance and direction separating two locations, used to quantify cross correlation. The cross variogram is defined as the variance of the difference between two variables of different types or attributes at two locations. The cross variogram generally increases with distance, and is described by nugget, sill, and range parameters.

cross-reference database

A database containing tables with information defining the mapping between a data source schema and an output geodatabase schema. Cross-reference databases are used by the PLTS data loader to batch populate a geodatabase from a variety of sources.

cross-tile indexing

A technique for indexing features that cross tile boundaries in a map library by storing them as one or more features in each tile, instead of storing them each as a single feature.

CSDGM

A publication authored by the FGDC that specifies the information content of metadata for digital geospatial datasets. The purpose of the standard is to provide a common set of terminology and definitions for concepts related to the metadata. All U.S. government agencies (federal, state, and local) that receive federal funds to create metadata must follow this standard.

CSS

Acronym for Cascading Style Sheets. A standard for defining the layout or presentation of an HTML or XML document. Style information includes font size, background color, text alignment, and margins. Multiple style sheets may be applied to "cascade" over previous style settings, adding to or overriding them. The World Wide Web Consortium maintains the CSS standard.

cubic convolution

A technique for resampling raster data in which the average of the nearest 16 cells is used to calculate the new cell value.

cull

In ArcScene and ArcGlobe, to selectively choose not to draw one side of an areal feature.

cultural feature

A human-made feature represented on a map, such as a building, road, tower, or bridge.

cultural geography

The field of geography concerning the spatial distribution and patterns created by human cultures and their effects on the earth.

curb approach

In network analysis, a network location property that models a path for approaching a stop from a specific side based on edge direction. For example, a school bus must approach a school from its door side so that students exiting the bus will not have to cross the street. There are three types of curb approaches: left, right, or both.

current cadastral fabric

In Survey Analyst - Cadastral Editor, the most up-to-date legal state of the cadastral fabric.

current coordinate

In Survey Analyst for field measurements, the single coordinate for a survey point that is the best representation for its location within each project. A current coordinate is required when the same project computes or imports more than one coordinate for a particular survey point.

current task

During editing in ArcMap, a setting in the Task drop-down list that determines which operation the sketch construction tools will perform. Examples of edit tasks include creating new features and modifying existing features. The edit task is set by clicking a task in the Task drop-down list.

current workspace

A user-specified path to a container for file-based geographic data, set in the Environment Settings dialog box. Data from the current workspace can be accessed from any tool dialog box (including script and model dialog boxes), or at the command line simply by typing its name.

curve fitting

Converting short connected straight lines into smooth curves to represent features such as rivers, shorelines, and contour lines. The curves that result pass through or close to the existing points.

custom behavior

A set of methods, functions or operations associated with a database object that has been specifically created or overridden by a programmer.

custom feature

In geodatabases, a feature with specialized behavior instantiated in a class by a programmer.

custom functionality

A modification to or enhancement of standard software functionality to meet a specific user's needs.

custom group layer

A layer created in ArcMap using the ArcGIS Image Server extension. Custom group layers display the contents of an image service definition, including the footprint, boundary, seamline and preview raster layer.

custom object

An object with custom behavior provided by a developer.

custom tool

In geoprocessing, a tool created by a user and added to a toolset and/or toolbox. Custom tools may only be added to custom toolsets and/or toolboxes.

custom toolset

In geoprocessing, a subset of a toolbox created by a user to hold custom tools or a group of frequently used tools.

customer market analysis

A type of market analysis that focuses on data about customers, rather than about a store or stores. An example is desire line analysis.

customer profiling

A process that establishes common demographic characteristics for a set of customers within a geographic area.

customer prospecting

A type of market analysis that locates regions with appropriate demographic characteristics for targeting new customers.

cut/fill

An ArcGIS Spatial Analyst and 3D Analyst function that summarizes areas and volumes of change between two surfaces.

cycle

A set of lines forming a closed polygon.

cylindrical projection

A projection that transforms points from a spheroid or sphere onto a tangent or secant cylinder. The cylinder is then sliced from top to bottom and flattened into a plane.

To the top

D

daemon

In programming, a process that continuously runs in the background, without being explicitly implemented, and performs a specified operation at predefined times or in response to certain events. Daemon is a UNIX term; the Windows equivalent is a system agent or service.
 

dangle

The endpoint of a dangling arc.
 

dangle length

In ArcInfo coverages, the minimum length allowed for dangling arcs by the clean process, which removes dangling arcs shorter than the dangle tolerance.
 

dangle tolerance

In ArcInfo coverages, the minimum length allowed for dangling arcs by the clean process, which removes dangling arcs shorter than the dangle tolerance.
 

dangling arc

An arc having the same polygon on both its left and right sides and having at least one node that does not connect to any other arc. It often occurs where a polygon does not close properly, where arcs do not connect properly (an undershoot), or where an arc was digitized past its intersection with another arc (an overshoot). A dangling arc is not always an error; for example, it can represent a cul-de-sac in a street network.
 

dangling node

The endpoint of a dangling arc.
 

dasymetric mapping

A technique in which attribute data that is organized by a large or arbitrary area unit is more accurately distributed within that unit by the overlay of geographic boundaries that exclude, restrict, or confine the attribute in question. For example, a population attribute organized by census tract might be more accurately distributed by the overlay of water bodies, vacant land, and other land-use boundaries within which it is reasonable to infer that people do not live.
 

data

Any collection of related facts arranged in a particular format; often, the basic elements of information that are produced, stored, or processed by a computer.
 

data capture

Any operation that converts GIS data into computer-readable form. Geographic data can be captured by being downloaded directly into a GIS from sources such as remote-sensing or GPS data, or it can be digitized, scanned, or keyed in manually from paper maps or photographs.
 

data change message

In ArcGIS, a message containing any inserts, updates, and deletes applied to a replica. These messages are used to synchronize replicas in a disconnected environment.
 

data conversion

The process of translating data from one format to another.
 

data definition language

A set of SQL statements that can be used either interactively or within a programming language to create a new database, set permissions on it, and define its attributes.
 

data dictionary

A catalog or table containing information about the datasets stored in a database. In a GIS, a data dictionary might contain the full names of attributes, meanings of codes, scale of source data, accuracy of locations, and map projections used.
 

data element

The smallest unit of information used to describe a particular characteristic of a spatial dataset. A data element is a logically primitive description that cannot be further subdivided.
 

data file

A file that holds text, graphics, or numbers.
 

data format

The structure used to store a computer file or record.
 

data frame

A map element that defines a geographic extent, a page extent, a coordinate system, and other display properties for one or more layers in ArcMap. A dataset can be represented in one or more data frames. In data view, only one data frame is displayed at a time; in layout view, all a map's data frames are displayed at the same time. Many cartography texts use the term "map body" to refer to what ESRI calls a data frame.
 

data integration

The process of sharing and combining data between two organizations or systems.
 

data integrity

The degree to which the data in a database is accurate and consistent according to data model and data type.
 

data logger

A lightweight, handheld field computer used to store data collected by a GPS receiver.
 

Data Manager Web Service

A SOAP ArcWeb service that allows users to upload their own point, line, or polygon data and attribute information to use in custom map and spatial query data sources.
 

data message

Information in a satellite's GPS signal that reports its orbital position, operating health, and clock corrections.
 

data model

In GIS, a mathematical construct for representing geographic objects or surfaces as data. For example, the vector data model represents geography as collections of points, lines, and polygons; the raster data model represents geography as cell matrixes that store numeric values; and the TIN data model represents geography as sets of contiguous, nonoverlapping triangles.
 

data product

In ArcWeb Services, a collection of layers that has a single credit cost. Every data layer has an associated data product.
 

data recorder

A lightweight, handheld field computer used to store data collected by a GPS receiver.
 

data repository

A repository structure, physical or virtual, that collects, stores, and disseminates information, metadata, and data. A clearinghouse provides widespread access to information and is generally thought of as reaching or existing outside organizational boundaries.
 

data sharing

Making data available and accessible to organizations or individuals other than the creator of the data.
 

data source

Any data. Data sources may include coverages, shapefiles, rasters, or feature classes.
 

data structure

The organization of data within a specific computer system that allows the data to be stored and manipulated effectively; a representation of a data model in computer form.
 

data synchronization

The process of applying data changes from a replica to the relative replica in a replica pair. Data changes include row or feature inserts, updates, and deletes. Synchronization can be performed in one or both directions between a replica pair.
 

data transfer

The process of moving data from one system to another or from one point on a network to another.
 

data type

The attribute of a variable, field, or column in a table that determines the kind of data it can store. Common data types include character, integer, decimal, single, double, and string.
 

data view

An all-purpose view in ArcMap and ArcReader for exploring, displaying, and querying geographic data. This view hides all map elements, such as titles, north arrows, and scale bars.
 

database

One or more structured sets of persistent data, managed and stored as a unit and generally associated with software to update and query the data. A simple database might be a single file with many records, each of which references the same set of fields. A GIS database includes data about the spatial locations and shapes of geographic features recorded as points, lines, areas, pixels, grid cells, or TINs, as well as their attributes.
 

database administrator

The person who manages a database. Database administration includes user setup, security, backup and recovery procedures for data, and optimization of physical data storage for best performance.
 

database connection

A link to a database from a software application. Database connections have two states: connected to or disconnected from the database. Deletion of a database connection only deletes the connection itself, not the database or its contents. Creation of a database connection requires selection of a data provider for data retrieval.
 

database design

The development of the conceptual, logical, and physical structures of a database in order to meet user requirements.
 

database generalization

The abstraction, reduction, and simplification of features and feature classes for deriving a simpler model of reality or decreasing stored data volumes.
 

database management system

A set of software applications used to create and maintain databases according to a schema. Database management systems provide tools for adding, storing, changing, deleting, and retrieving data.
 

database role

The database permissions category assigned to a group of users who perform the same types of tasks and, therefore, require the same level of database access. Database roles are used by database administrators to simplify the administration of user privileges.
 

database statistics

Mathematically calculated data that describes the state of a database and which the database management system (DBMS) uses to optimize query response.
 

database support

The proprietary database platforms supported by a program or component.
 

data-driven ring analysis

A type of market analysis primarily used to look at competing sites or to select potential new locations.
 

dataflow

The route of data passage through a system.
 

dataset

Any collection of related data, usually grouped or stored together.
 

dataset precision

The mathematical exactness or detail with which a value is stored within a dataset, based on the number of significant digits that can be stored for each coordinate.
 

datasnooping

In Survey Analyst, the process of testing each measurement using the W-test.
 

datum

The reference specifications of a measurement system, usually a system of coordinate positions on a surface (a horizontal datum) or heights above or below a surface (a vertical datum).
 

datum level

A surface to which heights, elevations, or depths are referenced.
 

datum plane

A surface to which heights, elevations, or depths are referenced.
 

datum points

In Survey Analyst for field measurements, survey points that are not defined by computations, but that are the input data for the initial computations in a sequence of computations.
 

datum shift

A systematic conversion of the latitude-longitude values for a set of points from one geographic coordinate system to equivalent values in another geographic coordinate system. Depending on the geographic coordinate systems involved, the transformation can be accomplished in various ways. Typically, equations are used to model the position and orientation of the "from" and "to" geographic coordinate systems in three-dimensional coordinate space; the transformation parameters may include translation, rotation, and scaling. Other methods, including one used in transformations between NAD 1927 and NAD 1983, use files in which the differences between the two geographic coordinate systems are given for a set of coordinates; the values of other points are interpolated from these.
 

datum transformation

A systematic conversion of the latitude-longitude values for a set of points from one geographic coordinate system to equivalent values in another geographic coordinate system. Depending on the geographic coordinate systems involved, the transformation can be accomplished in various ways. Typically, equations are used to model the position and orientation of the "from" and "to" geographic coordinate systems in three-dimensional coordinate space; the transformation parameters may include translation, rotation, and scaling. Other methods, including one used in transformations between NAD 1927 and NAD 1983, use files in which the differences between the two geographic coordinate systems are given for a set of coordinates; the values of other points are interpolated from these.
 

dbf

A database file format. In the ArcWeb Services Web site, users can upload data into Builder as either a DBF file or a shapefile (SHP).
 

DBF file

A database file format. In the ArcWeb Services Web site, users can upload data into Builder as either a DBF file or a shapefile (SHP).
 

DBMS

A set of software applications used to create and maintain databases according to a schema. Database management systems provide tools for adding, storing, changing, deleting, and retrieving data.
 

DCOM

Acronym for Distributed Component Object Model. Extends COM to support communication among objects on different computers on a network.
 

DDL

A set of SQL statements that can be used either interactively or within a programming language to create a new database, set permissions on it, and define its attributes.
 

dead reckoning

A navigation method of last resort that uses the most recently recorded position of a ship or aircraft, along with its speed and drift, to calculate a new position.
 

debug

To test for, detect, and correct errors in a computer program or component.
 

decimal degrees

Values of latitude and longitude expressed in decimal format rather than in degrees, minutes, and seconds.
 

decision support system

A computer program that includes data presentation and modeling tools that help people understand problems and find solutions.
 

declination

In a spherical coordinate system, the angle between the equatorial plane and a line to a point somewhere on the sphere.
 

deeply stateful application

An application that uses the GIS server to maintain application state by changing the state of a server object or its related objects. Deeply stateful applications require nonpooled server objects.
 

default cadastral fabric

In Survey Analyst - Cadastral Editor, the most up-to-date version of the cadastral fabric in the database that corresponds to the default version in the database. The default cadastral fabric does not represent the current legal state of the cadastral fabric.
 

default interface

When a COM object is created, the interface that is returned automatically if no other interface is specified. Most ArcObjects classes specify IUnknown as the default interface.
 

default junction type

In geometric networks, the user-established junction type that automatically connects two edges in the absence of a current user choice. An edge may also have a default end junction type, used for the free ends of new edges.
 

default style

The original style that is used to symbolize a layer class in ArcWeb Services. Symbols can be overwritten in a map data source.
 

defined study area

A study area with a defined boundary, such as a city.
 

definition query

In ArcMap, a request that examines feature or tabular attributes based on user-selected criteria and displays only those features or records that satisfy the criteria.
 

deflection

The creation of a segment at an angle relative to an existing segment.
 

degree

A unit of angular measure represented by the symbol °. The earth is divided into 360 degrees of longitude and 180 degrees of latitude.
 

degree slope

One method for representing the measurement of an inclined surface. The steepness of a slope may be measured from 0 to 90 degrees.
 

degrees-minutes-seconds

The unit of measure for describing latitude and longitude. A degree is 1/360th of a circle. A degree is further divided into 60 minutes, and a minute is divided into 60 seconds.
 

Delaunay triangles

The components of Delaunay triangulation. Delaunay triangles cannot exist alone; they must exist as part of a set or collection that is typically referred to as a triangulated irregular network (TIN). A circle circumscribed through the three nodes of a Delaunay triangle will not contain any other points from the collection in its interior.
 

Delaunay triangulation

A technique for creating a mesh of contiguous, nonoverlapping triangles from a dataset of points. Each triangle's circumscribing circle contains no points from the dataset in its interior. Delaunay triangulation is named for the Russian mathematician Boris Nikolaevich Delaunay.
 

deletes table

The geodatabase system table, created when a feature class or table is registered as versioned, that maintains information on all rows that have been deleted or updated.
 

delimiter

A character, such as a space or comma, that separates words or values.
 

delta database

A file that contains data edits that can be exchanged between geodatabases or between geodatabases and other data stores. The edits can come from a checkout geodatabase, modified rows between source and target versions, or a custom application. Supported delta file formats are XML (delta XML file) and delta database (.mdb file).
 

delta file

A file that contains data edits that can be exchanged between geodatabases or between geodatabases and other data stores. The edits can come from a checkout geodatabase, modified rows between source and target versions, or a custom application. Supported delta file formats are XML (delta XML file) and delta database (.mdb file).
 

delta table

One of two geodatabase system tables—the adds and deletes tables—created for a feature class or table when it is registered as versioned. These tables record changes made to a version during editing.
 

DEM

Acronym for digital elevation model. The representation of continuous elevation values over a topographic surface by a regular array of z-values, referenced to a common datum. DEMs are typically used to represent terrain relief.
 

demographics

The statistical characteristics (such as age, birth rate, and income) of a human population.
 

demography

The statistical study of human populations, especially their locations, distribution, economic statistics, and vital statistics.
 

densify

To add vertices to a line at specified distances without altering the line's shape.
 

densitometer

An instrument for measuring the opacity of translucent materials such as photographic negatives and optical filters.
 

density

In spatial measurements, the quantity per unit area or length.
 

density slicing

A technique normally applied to a single-band monochrome image for highlighting areas that appear to be uniform in tone, but are not. Grayscale values (0-255) are converted into a series of intervals, or slices, and different colors are assigned to each slice. Density slicing is often used to highlight variations in vegetation.
 

dependent variable

The variable representing the process being predicted or modeled, such as crime, foreclosure, or rainfall. The dependent variable is a function of the independent variables. Regression can be used to predict the dependent variable, using known (observed) values to build (calibrate) the regression model. In the regression equation, the dependent variable appears on the left side of the equal sign.
 

deployment

The installation of a component or application on a target machine.
 

depot

In ArcGIS Network Analyst, a network location used to represent a starting, stopping, or renewal location for routes in vehicle routing problem (VRP) analysis. Users can specify multiple depots. Depots are used as locations for loading/unloading vehicles within the fleet.
 

depot visit

In ArcGIS Network Analyst, an object used to represent a single visit to a specific depot in vehicle routing problem (VRP) analysis. A depot visit may occur at the start of a route, the end of the route, or as a renewal midway along a route.
 

depression contour

On a topographic map, concentric contour lines drawn with hachures to indicate a closed depression or basin. Concentric contour lines drawn without hachure marks indicate a hill.
 

depth contour

A line on a map connecting points of equal depth below a hydrographic datum.
 

depth curve

A line on a map connecting points of equal depth below a hydrographic datum.
 

derived data

In ModelBuilder, data created by running a geoprocessing operation on existing data. Derived data from one process can serve as input data for another process.
 

derived value

In ModelBuilder, data created by running a geoprocessing operation on existing data. Derived data from one process can serve as input data for another process.
 

descending node

The point at which a satellite traveling north to south crosses the equator.
 

descriptive data

Tabular or textual data describing the geographic characteristics of features.
 

descriptor

A type of attribute for network elements that cannot be apportioned. The value of a descriptor stays the same through the length of an edge element in a network dataset. Descriptors describe characteristics of the element; for example, the number of lanes for a particular road in a road network.
 

designated market area

A television market as defined by Nielsen Media Research. Most DMAs correspond to whole counties, but there are a few exceptions where counties are split into different DMAs.
 

desire-line analysis

A type of market analysis that draws lines from a set of geocoded points (usually customers) to a single, central point (usually a store). Desire lines can be weighted.
 

desktop GIS

Mapping software that is installed onto and runs on a personal computer and allows users to display, query, update, and analyze data about geographic locations and the information linked to those locations.
 

destination

The secondary object in a relationship class, such as a table containing attributes associated with features in a related table.
 

destination table

In ArcView 3.x, one of the two tables involved in a join operation. The destination table must be the active table; the attributes of the source (inactive) table are appended to it.
 

Detail page

One of two types of pages in the Survey Analyst Survey Explorer. The Detail page displays a detailed view of individual survey objects.
 

determinate flow direction

A conclusively definitive line or course in which something is issuing or moving in a stream. For an edge feature, this occurs when the flow direction can be ascertained from the connectivity of a network, the locations of sources and sinks, and the enabled or disabled states of features.
 

deterministic model

In spatial modeling, a type of model or a part of a model in which the outcome is completely and exactly known based on known input; the fixed or nonrandom components of a spatial model. The spline and inverse distance weighted interpolation methods are deterministic since they have no random components. The kriging and cokriging interpolation methods may have a deterministic component, often called the trend.
 

detrending

The process of removing the trend from a spatial model by subtracting the trend surface (usually polynomial functions of the spatial x- and y-coordinates) from the original data values. The resulting detrended values are called residuals.
 

developable surface

A geometric shape such as a cone, cylinder, or plane that can be flattened without being distorted. Many map projections are classified in terms of these shapes.
 

developer product

Products that can be used on one machine, similar to single use products. Each developer product requires a unique registration number used to generate the authorization file. The Software Authorization Wizard is then used to enter the authorization file and unlock the software for use.
 

developer sample

A sample contained in the ArcGIS Developer Help system.
 

development environment

A software product used to write, compile, and debug components or applications.
 

device context

Represents a surface that can be drawn to, for example, a screen, bitmap, or printer. In ArcGIS, the Display abstract class is used to abstract a device context.
 

device coordinates

The coordinates shown on a digitizer or display, as opposed to those of a recognized datum or coordinate system.
 

DGIWG

Acronym for Digital Geographic Information Working Group. A group established in 1983 to develop standards for spatial data exchange among nations participating in the North Atlantic Treaty Organization (NATO). The goals of the group are interoperability and burden sharing among nations, and its membership has recently expanded beyond NATO nations. While DGIWG is not an official NATO body, its work on standards has been recognized by the NATO Geographic Conference (NGC).
 

DGPS

A technique for increasing the accuracy of GPS measurements by comparing the readings to two receivers—one roving and the other a fixed base station—and a known location.
 

DHTML

An extension to HTML that allows Web designers to make elements on a Web page interactive, rather than changeable only when the page is loaded.
 

dialog box

In geoprocessing, a form consisting of a tool's parameters.
 

diazo process

A way of quickly and inexpensively copying maps using a diazo compound, ultraviolet light, and ammonia.
 

difference image

In image processing, an image made by subtracting the pixel values of one image from those in another.
 

differential correction

A technique for increasing the accuracy of GPS measurements by comparing the readings to two receivers—one roving and the other a fixed base station—and a known location.
 

differential Global Positioning System

A technique for increasing the accuracy of GPS measurements by comparing the readings to two receivers—one roving and the other a fixed base station—and a known location.
 

diffusion

The spread of an innovation or technology use among a group of people or organizations.
 

DIGEST

Acronym for Digital Geographic Information Exchange Standard. A standard for spatial data transfer among nations, data producers, and data users. The Digital Geographic Information Working Group (DGIWG) developed the standard to support interoperability within and between nations and share the burden of digital data production. The standard addresses the exchange of raster, matrix, and vector data (and associated text) and a range of levels of topological structures.
 

digital

Represented in discrete, quantified units rather than continuously. Computers process and store information in digital form.
 

digital elevation model

The representation of continuous elevation values over a topographic surface by a regular array of z-values, referenced to a common datum. DEMs are typically used to represent terrain relief.
 

Digital Geographic Information Exchange Standard

A standard for spatial data transfer among nations, data producers, and data users. The Digital Geographic Information Working Group (DGIWG) developed the standard to support interoperability within and between nations and share the burden of digital data production. The standard addresses the exchange of raster, matrix, and vector data (and associated text) and a range of levels of topological structures.
 

Digital Geographic Information Working Group

A group established in 1983 to develop standards for spatial data exchange among nations participating in the North Atlantic Treaty Organization (NATO). The goals of the group are interoperability and burden sharing among nations, and its membership has recently expanded beyond NATO nations. While DGIWG is not an official NATO body, its work on standards has been recognized by the NATO Geographic Conference (NGC).
 

digital image

An image stored in binary form and divided into a matrix of pixels. Each pixel consists of a digital value of one or more bits, defined by the bit depth. The digital value may represent, but is not limited to, energy, brightness, color, intensity, sound, elevation, or a classified value derived through image processing. A digital image is stored as a raster and may contain one or more bands.
 

digital image processing

Any technique that changes the digital values of an image for the sake of analysis or enhanced display, such as density slicing or low- and high-pass filtering.
 

digital line graph

Data files containing vector representations of cartographic information derived from USGS maps and related sources. DLGs include information from the USGS planimetric map base categories such as transportation, hydrography, contours, and public land survey boundaries.
 

digital nautical chart

A nautical database developed from existing hard-copy charts, digital data, bathymetric survey information, imagery, and various raster data. DNCs are used by the U.S. military and its allies for marine navigation.
 

digital number

In a digital image, a value assigned to a pixel.
 

digital orthophoto quadrangle

A computer-generated, uniform-scale image created from an aerial photograph. Digital orthophoto quadrangles are true photographic maps in which the effects of tilt and relief are removed by a mathematical process called transformation or rectification. The uniform scale of a DOQ allows accurate measurement of distances.
 

digital orthophoto quarter quadrangle

A digital orthophoto quadrangle (DOQ) divided into four quadrants.
 

digital raster graphic

A raster image of a scanned USGS standard series topographic map, usually including the original border information, referred to as the map collar, map surround, or marginalia. Source maps are georeferenced to the surface of the earth, fit to the universal transverse Mercator (UTM) projection, and scanned at a minimum resolution of 250 dpi. The accuracy and datum of a DRG matches the accuracy and datum of the source map.
 

digital terrain elevation data

A format for elevation data, usually tiled in 1-degree cells, produced by the National Geospatial-Intelligence Agency and U.S. allies for military applications.
 

digital terrain model

The representation of continuous elevation values over a topographic surface by a regular array of z-values, referenced to a common datum. DEMs are typically used to represent terrain relief.
 

digitizer

A device connected to a computer, consisting of a tablet and a handheld puck, that converts positions on the tablet surface as they are traced by an operator to digital x,y coordinates, yielding vector data consisting of points, lines, and polygons.
 

digitizing

The process of converting the geographic features on an analog map into digital format using a digitizing tablet, or digitizer, which is connected to a computer. Features on a paper map are traced with a digitizer puck, a device similar to a mouse, and the x,y coordinates of these features are automatically recorded and stored as spatial data.
 

digitizing mode

A way of using a digitizing tablet in which locations on the tablet are mapped to specific locations on the screen. Moving the digitizer puck on the tablet surface causes the screen pointer to move to precisely the same position on the screen.
 

Dijkstra's algorithm

An algorithm that examines the connectivity of a network to find the shortest path between two points. Dijkstra's algorithm is named after the Dutch computer scientist Edsger Dijkstra (1930-2002).
 

dilution of precision

An indicator of satellite geometry for a constellation of satellites used to determine a position. Positions with a lower DOP value generally constitute better measurement results than those with higher DOP. Factors determining the total GDOP (geometric DOP) for a set of satellites include PDOP (positional DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and TDOP (time DOP).
 

DIME

Acronym for Dual Independent Map Encoding. A data storage format for geographic data developed by the U.S. Census Bureau in the 1960s. DIME-encoded data was stored in Geographic Base Files (GBF). The Census Bureau replaced the DIME format with Topologically Integrated Geocoding and Referencing (TIGER) in 1990.
 

dimension

A length of a certain distance and bearing.
 

dimension construction method

One of a number of procedures that dictate what type of dimension feature is created and the number of points required to complete the feature's geometry. Construction methods include simple aligned, aligned, linear, rotated linear, free aligned, and free linear.
 

dimension feature

In ArcMap, a special kind of geodatabase annotation that shows specific lengths or distances on a map. A dimension feature may indicate the length of a side of a building or land parcel, or it may indicate the distance between two features, such as a fire hydrant and the corner of a building.
 

dimension feature class

A geodatabase feature class that stores dimension features.
 

dimension style

Description of a dimension feature's symbology, what parts of it are drawn, and how it is drawn. Every time a new dimension feature is created, it is assigned a particular style according to its shared characteristics. A collection of dimension styles is associated with a dimension feature class. Styles for a dimension feature class are created, copied, and managed using ArcCatalog or the editing capabilities in ArcMap. Styles are then assigned to individual dimension features.
 

Dimensioning toolbar

A toolbar in ArcMap that facilitates the creation of dimension features.
 

DIP

Any technique that changes the digital values of an image for the sake of analysis or enhanced display, such as density slicing or low- and high-pass filtering.
 

direct connect

An ArcSDE connection that results in a two-tier configuration, in which the ArcSDE client application communicates directly with the database.
 

directed link

In ArcInfo Workstation, an arc between two nodes with one direction specified.
 

directed network flow

A network state in which edges have an associated direction of flow. In a directed network flow, the resource that traverses a network's components cannot choose a direction to take, as in hydrologic and utility systems.
 

direction

In an ArcGIS vertical coordinate system, an identifier that indicates whether z-values are positive up or positive down. Heights or elevations are usually positive up, against the force of gravity (indicated by +1). Depths are usually positive down, with the force of gravity (indicated by -1).
 

direction field

In Survey Analyst for field measurements, a field in the computation page that allows the entry of bearings or azimuths between an input survey point and a computed survey point.
 

directional filter

In image processing, an edge-detection filter that enhances those linear features in an image that are oriented in a particular direction.
 

directional influences

Natural or physical processes that affect a measured trait or attribute so that the magnitude of the effects on the attribute vary in different directions.
 

directory

An area of a computer disk that holds a set of data files, other directories, or both. Operating systems use directories to organize data. Directories are arranged in a tree structure, in which each branch is a subdirectory of its parent branch. The location of a directory is specified with a path—for example, C:\gisprojects\shrinkinglemurhabitatgrids.
 

Directory Service

An OpenLS ArcWeb service used to find points of interest and other entities around a given location.
 

Dirichlet tessellation

A partition of space into areas, or cells, that surround a set of geometric objects (usually points). These cells, or polygons, must satisfy the criteria for Delaunay triangles. All locations within an area are closer to the object it surrounds than to any other object in the set. Voronoi diagrams are often used to delineate areas of influence around geographic features. Voronoi diagrams are named for the Ukrainian mathematician Georgy Fedoseevich Voronoi (1868-1908).
 

dirty areas

Regions surrounding features that have been altered after the initial topology validation process and require additional topology validation to be performed to find any errors.
 

disabled feature

In geometric networks, an object or shape representing a geographic object through which flow is impossible.
 

disconnected editing

The process of copying data to another geodatabase, editing that data, then merging the changes with the data in the source or master geodatabase.
 

discrete data

Data that represents phenomena with distinct boundaries. Property lines and streets are examples of discrete data.
 

discrete digitizing

A method of digitizing in which points are placed individually to define a feature's shape.
 

discrete feature

A feature that has definite feature boundaries.
 

discrete raster

A raster that typically represents phenomena that have clear boundaries with attributes that are descriptions, classes, or categories. Generally, integers are used for the cell values. In a raster of land cover, for example, the value 1 might represent forestland, the value 2 urban land, and so on. It is assumed that the phenomena that each value represents fill the entire area of the cell. Rasters representing land use, political boundaries or ownership are examples of discrete rasters.
 

disk

A storage medium for recording digital information, consisting of a round, flat, spinning plate coated with a magnetic material.
 

disk cache

In ArcGlobe, the folder on a computer's disk drive where ArcGlobe stores layer cache files.
 

DispID binding

A type of early binding in which DispID properties and methods are accessed at compile time, so there's no need to call them at run time. DispID binding is used for components that have type libraries but don't support vTable binding. MapObjects uses DispID binding.
 

displacement link

In ArcGIS, a link created to define the source and destination coordinates for a spatial adjustment. Links are represented as arrows with the arrowhead pointing toward the destination location. Links can be created manually or loaded from a link file.
 

displacement vector

In Survey Analyst - Cadastral Editor, the difference in the coordinates of a point between successive least-squares adjustments. A set of displacement vectors is recorded for a point when the point is part of a least-squares adjustment. Adjustment vectors can be used to track spatial changes in the cadastral fabric over time, and to adjust associated feature classes to match the most up to date cadastral fabric location.
 

display

Often used to refer to subclasses of the Display abstract class. For example, "when drawing to the display" means when drawing to any of the display coclasses; "the display pipeline" refers to the sequence of calls made when drawing occurs.
 

display projection

The coordinate system used for displaying geographic data. Examples include the data frame in ArcMap and the view in ArcView GIS.
 

display scale

The scale at which data is rendered on a computer screen or on a printed map.
 

display type

The mode of command representation on a computer screen. The display type controls whether you see a command's image, its caption, or both when it appears on a toolbar or in a menu.
 

display unit

The unit of measure used to render dimensions of shapes, distance tolerances, and offsets on a computer screen or on a printed map. Although they are stored with consistent units in the dataset, users can choose the units in which coordinates and measurements are displayed—for example, feet, miles, meters, or kilometers.
 

dissemination

The spread of an innovation or technology use among a group of people or organizations.
 

dissolve

A geoprocessing command that removes boundaries between adjacent polygons that have the same value for a specified attribute.
 

dissolve route events

In linear referencing, a procedure that combines event records in tables where there are events on the same route that have the same value for specified fields. The Dissolve Route Events tool combines events when there is measure overlap, and is available for both line and point event tables.
 

distance

The measure of separation between two entities or locations that may or may not be connected, such as two points. Distance is differentiated from length, which implies a physical connection between entities or locations.
 

distance decay

A mathematical representation of the effect of distance on the accessibility of locations and the number of interactions between them, reflecting the notion that demand drops as distance increases. Distance decay can be expressed as a power function or as an exponential function.
 

distance field

In the Survey Analyst for field measurements Survey Explorer, a field for entering distance for use in a computation.
 

distance unit

The unit of measurement for distance, such as feet, miles, meters, and kilometers.
 

distortion

On a map or image, the misrepresentation of shape, area, distance, or direction of or between geographic features when compared to their true measurements on the curved surface of the earth.
 

distortion circle

A graphical representation of the spatial distortion at a particular map location. The indicatrix is the figure that results when a circle on the earth's surface is plotted to the corresponding point on a map. The shape, size, and orientation of an indicatrix at any given point depend on the map projection used. In conformal (shape-preserving) projections, the indicatrix is a circle; in nonconformal projections, it is an ellipse at most locations. As a visual aid, indicatrices convey a general impression of distortion; as mathematical tools, they can be used to quantify distortion of scale and angle precisely. The indicatrix is named for Nicolas Auguste Tissot, the French mathematician who developed it.
 

Distributed Component Object Model

Extends COM to support communication among objects on different computers on a network.
 

distributed data

Data spread over multiple platforms or a network by a process referred to as replication.
 

distributed database

A database with records that are dispersed between two or more physical locations. Data distribution allows two or more people to be working on the same data in separate locations.
 

distribution

The frequency or amount at which a thing or things occur within a given area.
 

dithering

The approximation of shades of gray or colors in a computer image made by arranging pixels of black and white or other colors in alternate layers. The technique gives the appearance of a wider range of color or shades than is actually present in the image. It is widely used to improve the appearance of images displayed on devices with limited color palettes.
 

diurnal

Daily, as in the revolution of the earth.
 

diurnal arc

The apparent path from rise to set made by a heavenly body across the sky.
 

DLG

Acronym for digital line graph. Data files containing vector representations of cartographic information derived from USGS maps and related sources. DLGs include information from the USGS planimetric map base categories such as transportation, hydrography, contours, and public land survey boundaries.
 

DLL

Acronym for dynamic-link library. A type of file that stores shared code to be used by multiple programs (a "code library"). Programs access the shared code by linking to the DLL file when they run, a process referred to as dynamic linking. The DLL file must be registered for other programs to locate it.
 

DMA

Acronym for Designated Market Area. A television market as defined by Nielsen Media Research. Most DMAs correspond to whole counties, but there are a few exceptions where counties are split into different DMAs.
 

DMS

The unit of measure for describing latitude and longitude. A degree is 1/360th of a circle. A degree is further divided into 60 minutes, and a minute is divided into 60 seconds.
 

DNC

Acronym for digital nautical chart. A nautical database developed from existing hard-copy charts, digital data, bathymetric survey information, imagery, and various raster data. DNCs are used by the U.S. military and its allies for marine navigation.
 

DNS

Acronym for domain name system. The Internet distributed system that stores IP addresses and domain names to assist with the routing of network traffic.
 

dockable window

A window that can exist in a floating state or be attached to the main application window.
 

docking

Moving a floating toolbar or window to a fixed location in the graphical user interface.
 

document

A component of an ArcView 3.x project. Each document type (view, table, chart, layout, script) has its own window and interface.
 

documentation

Supporting information for software data and tools. Documentation may be descriptive or instructional, and is published in a variety of formats, including user's guides and manuals, desktop help systems, embedded or context-sensitive help, tutorials, reports, and metadata.
 

Documentation Editor

In geoprocessing, the interface used to write documentation for tools, toolsets, toolboxes, and processes within a model.
 

domain

The range of valid values for a particular metadata element.
 

domain name

The unique name of a computer system on the Internet, such as "esri.com."
 

domain name system

The Internet distributed system that stores IP addresses and domain names to assist with the routing of network traffic.
 

dongle

A small hardware device that provides the unique number used in the generation of a license file. The key is plugged into either the parallel or USB port on the License Manager Server. UNIX users of ArcGIS software do not need a hardware key. Hardware keys are also called dongles.
 

donut rings

A method of defining the rings in an analysis so that the values inside the rings are exclusive. For example, in an analysis with three donut rings and 10 households in each, the total number of households for each ring would be 10.
 

DOP

Acronym for dilution of precision. An indicator of satellite geometry for a constellation of satellites used to determine a position. Positions with a lower DOP value generally constitute better measurement results than those with higher DOP. Factors determining the total GDOP (geometric DOP) for a set of satellites include PDOP (positional DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and TDOP (time DOP).
 

Doppler shift

The apparent change in frequency of sound or light waves caused by the relative motion between a source and an observer. As they approach one another, the frequency increases; as they draw apart, the frequency decreases. The Doppler shift is also known as the Doppler effect, and is named for Austrian physicist and mathematician Christian Andreas Doppler.
 

Doppler-aided GPS

Signal processing that uses a measured Doppler shift to help the receiver track the GPS signal.
 

DOQ

Acronym for digital orthophoto quadrangle. A computer-generated, uniform-scale image created from an aerial photograph. Digital orthophoto quadrangles are true photographic maps in which the effects of tilt and relief are removed by a mathematical process called transformation or rectification. The uniform scale of a DOQ allows accurate measurement of distances.
 

DOQQ

Acronym for digital orthophoto quarter quadrangle. A digital orthophoto quadrangle (DOQ) divided into four quadrants.
 

dot density map

A quantitative, thematic map on which dots of the same size are randomly placed in proportion to a numeric attribute associated with an area. Dot density maps convey the intensity of an attribute.
 

dot distribution map

A map that uses dots or other symbols to represent the presence, quantity, or value of a phenomenon or thing in a specific area. In a dot distribution map, the size of the dots is scaled in proportion to the intensity of the variable.
 

dot screen

A photographic film covered with uniformly sized, evenly spaced dots used to break up a solid color, producing an apparently lighter color.
 

dots per inch

A measure of the resolution of scanners, printers, and graphic displays. The more dots per inch, the more detail can be displayed in an image.
 

double precision

The level of coordinate exactness based on the possible number of significant digits that can be stored for each coordinate. Datasets can be stored in either single or double precision. Double-precision geometries store up to 15 significant digits per coordinate (typically 13 to 14 significant digits), retaining the accuracy of much less than 1 meter at a global extent.
 

double-coordinate precision

The level of coordinate exactness based on the possible number of significant digits that can be stored for each coordinate. Datasets can be stored in either single or double precision. Double-precision geometries store up to 15 significant digits per coordinate (typically 13 to 14 significant digits), retaining the accuracy of much less than 1 meter at a global extent.
 

Douglas-Peucker algorithm

An algorithm that simplifies complex lines by reducing the number of points used to represent them. The Douglas-Peucker algorithm was developed by the Canadian geographers David H. Douglas and Thomas K. Peucker.
 

downstream

In network tracing, the direction along a line or edge that is the same as the direction of flow.
 

dpi

Acronym for dots per inch. A measure of the resolution of scanners, printers, and graphic displays. The more dots per inch, the more detail can be displayed in an image.
 

drafting

A method of drawing with pencil or pen and ink, used in cartographic reproduction.
 

drainage

All map features associated with the movement and flow of water, such as rivers, streams, and lakes.
 

draped layer

A layer in ArcGlobe that has been categorized to be draped on top of the globe surface.
 

draping

A perspective or panoramic rendering of a two-dimensional image superimposed onto a three-dimensional surface. For example, an aerial photograph might be draped over a digital elevation model (DEM) to create a realistic terrain visualization.
 

drawing priority

In 3D analysis, the order in which layers that occupy the same x,y,z positions are drawn in a scene. For example, if a road feature layer and an orthophoto are draped over the same terrain model, the roads and raster may appear patchy or broken up where they coincide. The drawing priority for the raster can be reduced so it will appear below the features. The drawing priority can only be changed for polygon features and surfaces.
 

DRG

Acronym for digital raster graphic. A raster image of a scanned USGS standard series topographic map, usually including the original border information, referred to as the map collar, map surround, or marginalia. Source maps are georeferenced to the surface of the earth, fit to the universal transverse Mercator (UTM) projection, and scanned at a minimum resolution of 250 dpi. The accuracy and datum of a DRG matches the accuracy and datum of the source map.
 

drift

The general pattern of z-values throughout a kriging model. The drift, or structure, forms the model's basic shape.
 

drive-time area

A zone around a map feature measured in units of time needed for travel by car. For example, a store's 10-minute drive-time area defines the area in which drivers can reach the store in 10 minutes or less.
 

drum scanner

A type of scanner in which a hard-copy image or map is attached to a cylinder that spins while a sensor captures a digital image from the surface of the page.
 

DTD

Acronym for document type definition. A set of rules that define the allowed structure and properties of XML documents.
 

DTED

Acronym for digital terrain elevation data. A format for elevation data, usually tiled in 1-degree cells, produced by the National Geospatial-Intelligence Agency and U.S. allies for military applications.
 

DTM

Acronym for digital elevation model. The representation of continuous elevation values over a topographic surface by a regular array of z-values, referenced to a common datum. DEMs are typically used to represent terrain relief.
 

Dual Independent Map Encoding

A data storage format for geographic data developed by the U.S. Census Bureau in the 1960s. DIME-encoded data was stored in Geographic Base Files (GBF). The Census Bureau replaced the DIME format with Topologically Integrated Geocoding and Referencing (TIGER) in 1990.
 

duplicate labels

Labels with identical content. Maplex for ArcGIS provides the option of labeling only a single feature out of a cluster of similar features. Identical labels will not be placed within the user-defined distance of a placed label.
 

dynamic binding

A COM technique that an application uses for determining an object's properties and methods at run time, rather than when the code is compiled. Late binding is generally used by scripting languages.
 

dynamic feature class

A feature class consisting of points associated with address elements in an address data table that change based on changes made to the address data table.
 

dynamic HTML

An extension to HTML that allows Web designers to make elements on a Web page interactive, rather than changeable only when the page is loaded.
 

dynamic segmentation

The process of computing the map locations of linearly referenced data (for example, attributes stored in a table) at run time so they can be displayed on a map, queried, and analyzed using a GIS. The dynamic segmentation process enables multiple sets of attributes to be associated with any portion of a line feature without segmenting the underlying feature. In the transportation field, examples of such linearly referenced data might include accident sites, road quality, and traffic volume.
 

dynamic style

In ArcWeb Services, a map style that changes based on the selected style sheet. Users can select from a set of defined dynamic styles for a map data source, but they cannot create dynamic styles.
 

dynamic-link library

A type of file that stores shared code to be used by multiple programs (a "code library"). Programs access the shared code by linking to the DLL file when they run, a process referred to as dynamic linking. The DLL file must be registered for other programs to locate it.

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E

early binding

A COM technique an application uses to access an object. In early binding, an object's properties and methods are discovered from an interface at compile time, instead of being checked at run time as in late binding. This difference often gives early binding performance benefits over late binding. There are two types of early binding: DispID binding and vTable binding.
 

earth-centered datum

A horizontal geodetic datum based on an ellipsoid that has its origin at the earth's center of mass. Examples are the World Geodetic System of 1984, the North American Datum of 1983, and the Geodetic Datum of Australia of 1994. The first uses the WGS84 ellipsoid; the latter two use the GRS80 ellipsoid. Geocentric datums are more compatible with satellite positioning systems, such as GPS, than are local datums.
 

easting

The distance east of the origin that a point in a Cartesian coordinate system lies, measured in that system's units.
 

eccentricity

A measure of how much an ellipse deviates from a circle, expressed as the ratio of the distance between the center and one focus of an ellipsoid to the length of its semimajor axis. The square of the eccentricity (e2) is commonly used with the semimajor axis a to define a spheroid.
 

ecliptic

The great circle formed by the intersection of the plane of the earth's orbit around the sun (or apparent orbit of the sun around the earth) and the celestial sphere.
 

ecological fallacy

The assumption that an individual from a specific group or area will exhibit a trait that is predominant in the group as a whole.
 

economic geography

The field of geography concerning the distribution and variation of economic factors by location, including how economic factors interact with geographic factors such as climate, land use, and geology.
 

edge

A line between two points that forms a boundary. In a geometric shape, an edge forms the boundary between two faces. In an image, edges separate areas of different tones or colors. In topology, an edge defines lines or polygon boundaries.
 

edge connectivity policy

In network datasets, a connectivity policy that defines how one edge may connect to another edge mid-span. There are two edge-edge connectivity policies: endpoint connectivity and any-vertex connectivity.
 

edge detection

A digital image processing technique for isolating edges in a digital image by examining it for abrupt changes in pixel value.
 

edge element

A line between two points that forms a boundary. In a geometric shape, an edge forms the boundary between two faces. In an image, edges separate areas of different tones or colors. In topology, an edge defines lines or polygon boundaries.
 

edge enhancement

A digital image processing technique for emphasizing the appearance of edges and lines in an image.
 

edge-edge rule

In geometric networks, a connectivity rule that defines how one edge may connect to another edge through a junction.
 

edge-junction cardinality

In connectivity relationships for networks, the number of edges of one type that may be associated with junctions of another type. Edge-junction cardinality defines a range of permissible connections that may occur in a one-to-many relationship between a single junction and many edges.
 

edge-junction rule

In geometric networks, a connectivity rule that defines how an edge may connect to a junction.
 

edgematching

A spatial adjustment process that aligns features along the edge of an extent to the corresponding features in an adjacent extent.
 

Edit Annotation tool

A tool on the Annotation toolbar that is used to manipulate geodatabase annotation. Text can be interactively moved, scaled, and rotated. Shortcut menu options allow control of the position, orientation, symbology, content, size, and style of text.
 

edit box

An entity that displays text entered by a user or derived from another source for editing purposes.
 

edit cache

A setting used in ArcMap that allows temporary storage of geodatabase or ArcIMS feature service features from a given map extent in the desktop computer's RAM, which may result in performance improvements in ArcMap for editing, feature rendering, and labeling.
 

edit mask

The portion of a coverage where the geometry (or geographical features) has been altered, but where topology has not yet been restored.
 

edit session

In ArcMap, the environment in which spatial and attribute editing take place. After starting an edit session, a user can modify feature locations, geometry, or attributes. Modifications are not saved unless the user explicitly chooses to save them.
 

edit sketch

In ArcMap, a temporary sketch that is used to perform a variety of tasks. Creating an edit sketch is a standard way to edit feature geometry.
 

edit task

During editing in ArcMap, a setting in the Task drop-down list that determines which operation the sketch construction tools will perform. Examples of edit tasks include creating new features and modifying existing features. The edit task is set by clicking a task in the Task drop-down list.
 

Editor toolbar

In ArcMap, a set of tools that allows the creation and modification of features and their attributes.
 

EDMS

Acronym for electronic document management system. A computer-based system for organizing, maintaining, and retrieving digital and hard-copy documents. An EDMS usually includes a check-in, check-out system for document tracking, versioning, and search-and-retrieval capabilities.
 

EDN

Acronym for ESRI Developer Network. A subscription program used to acquire ESRI software for developers, which includes a special program for supporting the ESRI developer community. EDN is intended to promote collaboration and interaction among GIS developers and ESRI staff.
 

EJB

The server-side component architecture for the J2EE platform. EJB enables development of distributed, transactional, secure, and portable Java applications.
 

elastic transformation

A procedure for adjusting the coordinates of all the data points in a dataset to allow a more accurate match between known locations and a few data points within the dataset. Rubber sheeting preserves the interconnectivity between points and objects through stretching, shrinking, or reorienting their interconnecting lines.
 

electromagnetic radiation

Energy that moves through space at the speed of light as different wavelengths of time-varying electric and magnetic fields. Types of electromagnetic radiation include gamma, x, ultraviolet, visible, infrared, microwave, and radio.
 

electromagnetic spectrum

The entire range of wavelengths (frequencies) over which electromagnetic radiation extends.
 

electronic atlas

A mapping system that displays but does not allow for the spatial analysis of data.
 

electronic document management system

A computer-based system for organizing, maintaining, and retrieving digital and hard-copy documents. An EDMS usually includes a check-in, check-out system for document tracking, versioning, and search-and-retrieval capabilities.
 

electronic navigational chart

A vector data product used for nautical navigation. ENC data is produced by nautical charting agencies throughout the world and uses the IHO (International Hydrographic Organization) S-57 standard for its database structure and attribution.
 

element

In geoprocessing in ArcGIS, a component of a model. Elements can be variables, such as input and derived data, or tools.
 

elevation

The vertical distance of a point or object above or below a reference surface or datum (generally mean sea level). Elevation generally refers to the vertical height of land.
 

elevation guide

A map element that displays a simplified representation of the terrain within a map's extent. Elevation guides are designed to provide a quick overview of topography, including the high and low points.
 

elevation layer

A layer in ArcGlobe that has been categorized to help define the geometry of the globe surface.
 

elevation tints

Hypsometric tint bands based on elevation ranges used in an elevation guide.
 

ellipse

A geometric shape described mathematically as the collection of points whose distances from two given points (the foci) add up to the same sum. An ellipse is shaped like a circle viewed obliquely.
 

ellipsoid

A three-dimensional, closed geometric shape, all planar sections of which are ellipses or circles. An ellipsoid has three independent axes, and is usually specified by the lengths a,b,c of the three semi-axes. If an ellipsoid is made by rotating an ellipse about one of its axes, then two axes of the ellipsoid are the same, and it is called an ellipsoid of revolution, or spheroid. If the lengths of all three of its axes are the same, it is a sphere.
 

ellipticity

A measure of how much an ellipse deviates from a circle, expressed as the ratio of the distance between the center and one focus of an ellipsoid to the length of its semimajor axis. The square of the eccentricity (e2) is commonly used with the semimajor axis a to define a spheroid.
 

embedded feature class

A multipoint feature class embedded into a terrain dataset. When a feature class is embedded, it is incorporated directly into the terrain pyramid and the terrain becomes the sole container of the data. Embedded feature classes can be used to reduce the amount of disk space required by mass point data such as lidar.
 

EMF

Acronym for Enhanced Metafile. A spool file format used in printing by the Windows operating system.
 

empirical

That property of a quantity that indicates that the quantity depends on data, observations, or experiment only; that is, it is not a model or part of a model. An empirical semivariogram is computed on data only, in contrast to a theoretical semivariogram model. 
 

enabled feature

In geometric networks, a network feature that allows flow to pass through it.
 

ENC

Acronym for electronic navigational chart. A vector data product used for nautical navigation. ENC data is produced by nautical charting agencies throughout the world and uses the IHO (International Hydrographic Organization) S-57 standard for its database structure and attribution.
 

enclosure

A file describing the contents of an item included in metadata. Enclosing files in metadata works the same way as enclosing files in an e-mail message.
 

encoding

The recording or reformatting of data into a computer format. Data may be encoded to reduce storage, increase security, or to transfer it between systems using different file formats. In GIS, analog graphic data, such as paper maps and images, are encoded into computer formats by scanning or digitizing.
 

end hatch definition

In linear referencing, a special type of hatch definition that draws hatch marks only at the low and high measure of a linear feature.
 

end offset

An adjustable value that dictates how far away from the end of a line an address location should be placed. Using an end offset prevents the point from being placed directly over the intersection of cross streets if the address happens to fall on the beginning or end of the street.
 

endpoint connectivity

In network datasets, a type of edge connectivity policy that states that an edge may only connect to another edge at its endpoints.
 

enhancement

In remote sensing, applying operations to raster data to improve appearance or usability by making specific features more detectable. Such operations can include contrast stretching, edge enhancement, filtering, smoothing, and sharpening.
 

enterprise geodatabase

A geodatabase managed in an RDBMS server by ArcSDE. Multiuser geodatabases can be very large and support multiple concurrent editors. They are supported on a variety of commercial RDBMS, including IBM DB2, IBM Informix, Oracle, Microsoft SQL Server, and PostgreSQL.
 

enterprise GIS

A geographic information system that is integrated through an entire organization so that a large number of users can manage, share, and use spatial data and related information to address a variety of needs, including data creation, modification, visualization, analysis, and dissemination.
 

Enterprise JavaBeans

The server-side component architecture for the J2EE platform. EJB enables development of distributed, transactional, secure, and portable Java applications.
 

envelope

The rectangle surrounding one or more geographical features in coordinate space, determined by the minimum and maximum coordinates in the x and y directions, as well as the ranges of any z- or m-values that the features may have. An envelope can be used to filter data for analysis.
 

environment settings

Settings that can apply to all tools within the application, all tools within a model or script, or a particular process within a model or script. Environment settings include current workspace, output spatial reference, output spatial grids, cell size, and tile size. They are generally set before running tools.
 

environment variable

A variable maintained by the operating system and shared among programs. Environment variables function as placeholders for environment information, such as a drive, path or file name.
 

environmental model

An abstract representation of a complex environmental process, emphasizing relationships and patterns in natural systems. Environmental models allow decision makers to better understand the effects of natural systems or the impact of human activities on natural systems.
 

EOBrowser

An ArcGIS utility application that can be used to investigate the contents of object libraries.
 

ephemeris

A table of the predicted positions of a satellite within its orbit for each day of the year, or for other regular intervals.
 

EPSG ID

A coordinate system identification created by the European Petroleum Survey Group.
 

equal competition area

A trade area boundary set halfway between a store or service point and its neighboring stores or service points.
 

equal-area classification

A data classification method that divides polygon features into groups so that the total area of the polygons in each group is approximately the same.
 

equal-area projection

A projection in which the whole of the map as well as each part has the same proportional area as the corresponding part of the earth. An equal-area projection may distort shape, angle, scale, or any combination thereof. No flat map can be both equal-area and conformal.
 

equal-interval classification

A data classification method that divides a set of attribute values into groups that contain an equal range of values.
 

equator

The parallel of reference that is equidistant from the poles and defines the origin of latitude values.
 

equatorial aspect

A planar (or azimuthal) projection with its central point located at the equator.
 

equidistant projection

A projection that maintains scale along one or more lines, or from one or two points to all other points on the map. Lines along which scale (distance) is correct are the same proportional length as the lines they reference on the globe. In the sinusoidal projections, for example, the central meridian and all parallels are their true lengths. An azimuthal equidistant projection centered on Chicago shows the correct distance between Chicago and any other point on the projection, but not between any other two points.
 

equivalent projection

A projection in which the whole of the map as well as each part has the same proportional area as the corresponding part of the earth. An equal-area projection may distort shape, angle, scale, or any combination thereof. No flat map can be both equal-area and conformal.
 

erase

In ArcInfo, a command that removes or deletes features from one coverage that overlap features in another coverage.
 

error

A measured, observed, calculated, or interpreted value that differs from the true value or the value that would be obtained by a perfect observer using perfect equipment and perfect methods under perfect conditions.
 

error propagation

In GIS data processing, the persistence of an error into new datasets calculated or created using datasets that originally contained errors. The study of error propagation is concerned with the effects of combined and accumulated errors throughout a series of data processing operations.
 

error table

A geodatabase table used by the GIS Data ReViewer to track error information through the quality control process. Defects are recorded, resolved and verified in the error table.
 

ESRI Adapters for IBM LAS

A translator that allows users to access ArcWeb Services through the IBM WebSphere Everywhere Access (WEA) Location Aware Services (LAS).
 

ESRI Developer Network

A subscription program used to acquire ESRI software for developers, which includes a special program for supporting the ESRI developer community. EDN is intended to promote collaboration and interaction among GIS developers and ESRI staff.
 

ESRI Grid

An ESRI data format for storing raster data that defines geographic space as an array of equally sized square cells arranged in rows and columns. Each cell stores a numeric value that represents a geographic attribute (such as elevation) for that unit of space. When the grid is drawn as a map, cells are assigned colors according to their numeric values. Each grid cell is referenced by its x,y coordinate location.
 

ESRI Maplex Label Engine

In Maplex for ArcGIS, extended software that allows finer control of how labels are placed.
 

ESRI Standard Label Engine

In ArcMap, the software used to place labels.
 

EsriMapCatalog.ser

A binary serialized file created in the ArcIMS 3.x AppServer directory to save site parameters. This file has now been replaced by ArcIMSSite.sez.
 

EsriMapCookies.ser

A binary serialized file created in the ArcIMS 3.x AppServer directory to store ArcIMS Folders and any submitted MapNotes and EditNotes. This file has now been replaced by ArcIMSFolders.sez.
 

estimation

In spatial modeling, the process of forming a statistic from observed data to assign optimal parameters in a model or distribution.
 

Euclidean distance

The straight-line distance between two points on a plane. Euclidean distance, or distance "as the crow flies," can be calculated using the Pythagorean theorem.
 

Euclidean distance analysis

In ArcGIS Spatial Analyst, a description of each raster cell's relationship to the closest source.
 

evaluator

A function that determines attribute values for network elements in a network dataset. If a network source does not have an evaluator, the default evaluator for its element type is used.
 

event

A geographic location stored in tabular rather than spatial form. Event types include address events, route events, x,y events, and temporal events.
 

event handling

Watching for events that are broadcast by another class, and taking action when they occur.
 

event layer

In ArcGIS, a layer created from an event table.
 

event location

A geographic location stored in tabular rather than spatial form. Event types include address events, route events, x,y events, and temporal events.
 

event overlay

In linear referencing, an operation that produces a route event table that is the logical intersection or union of two input route event tables. Event overlay is one way to perform line-on-line, line-on-point, and event point-on-point overlays.
 

event table

A data source containing location information in tabular format (called events) that is used to create a spatial dataset. For example, an event table might contain x,y coordinates or routes.
 

event theme

In ArcView 3.x, a spatial data theme created from an event table.
 

event transform

In linear referencing, an operation that produces a new table by copying and transforming events from one route reference to another. This allows the events to be used with a route reference having different route identifiers and/or measures.
 

exception

An error that is an acceptable violation of a topology rule. In ArcMap, for example, a cul-de-sac is a legitimate exception to the rule that prohibits dangles.
 

executable file

A binary file containing a program that can be run as a stand-alone application. In the Microsoft Windows program, executable files are designated with an .exe extension.
 

exit state

The condition of a tool upon closure. If a tool fails due to a programming bug or command failure, the exit state will be "failed." 
 

explanatory variable

One or a set of variables used to model or predict the dependent variable. For example, a prediction of annual purchases for a proposed store (the dependent variable) might include independent variables representing the number of potential customers, distance to competition, store visibility, and local spending patterns. In the regression equation, independent variables appear on the right side of the equal sign and are often referred to as explanatory variables.
 

explode

An editing process that separates a multipart feature into its component features, which become independent features.
 

exponent

In mathematics, a number that indicates how many times a base value is multiplied by itself. Exponents are usually indicated with superscripts.
 

export

To move data from one computer system to another, and often, in the process, from one file format to another.
 

exposure station

In aerial photography, each point in the flight path at which the camera exposes the film.
 

expression

A sequence of operands and operators constructed according to the syntactic rules of a symbolic language that evaluates to a single number, string, or value.
 

Extended Entity Data

In AutoCAD, extra optional data attached to an AutoCAD drawing element.
 

extended postal code

An enhanced ZIP Code that consists of the five-digit ZIP Code plus four additional digits that identify a specific geographic segment within the five-digit delivery area, such as a city block, office building, or other unit.
 

Extensible Markup Language

Developed by the W3C, a standardized general purpose markup language for designing text formats that facilitates the interchange of data between computer applications. XML is a set of rules for creating standard information formats using customized tags and sharing both the format and the data across applications.
 

Extensible Style Language

A set of standards for defining XML document presentation and transformation. An XSL style sheet may contain information about how to display tagged content in an XML document, such as font size, background color, and text alignment. An XSL style sheet may also contain XSLT code that describes how to transform the tagged content in an XML document into an output document with another format. The W3C maintains the XSL standards.
 

Extensible Style Language Transformations

A language for transforming the tagged content in an XML document into an output document with another format. An XSL style sheet contains the XSLT code that defines each transformation to be applied. Transforming a document requires the original XML document, an XSL document containing XSLT code, and an XSLT processor (parser) to execute the transformations. The W3C maintains the XSLT standard.
 

extension

In ArcGIS, an optional software module that adds specialized tools and functionality to ArcGIS Desktop. ArcGIS Network Analyst, ArcGIS StreetMap, and ArcGIS Business Analyst are examples of ArcGIS extensions.
 

extent

The minimum bounding rectangle (xmin, ymin and xmax, ymax) defined by coordinate pairs of a data source. All coordinates for the data source fall within this boundary.
 

extent rectangle

A rectangle that is displayed in one data frame, showing the size and position of another data frame.
 

external polygon

In coverages, the first record in a polygon attribute table, representing the area beyond the outer boundary of the coverage.
 

extract server

A private ArcIMS virtual server that clips data and saves it to a Zip file.
 

Extract wizard

An ArcToolbox wizard that selects features from a coverage based on attribute values to create a new coverage.
 

extraction guide

A specification that defines parameters for feature extraction and attribution. Specifications typically include the size of features to be collected, density of feature collection, scale ranges, and attribute assignment.
 

extrapolation

Using known or observed data to infer or calculate values for unobserved times, locations or other variables outside a sampled area. In the absence of data, extrapolation is a common method for making predictions, but it is not always accurate. For example, based on observed economic indicators, an economist can make predictions about the state of the economy at a future time. These predictions may not be accurate because they cannot take into account seemingly random events such as natural disasters.
 

extrusion

The process of projecting features in a two-dimensional data source into a three-dimensional representation: points become vertical lines, lines become planes, and polygons become three-dimensional blocks. Uses of extrusion include showing the depth of well point features or the height of building-footprint polygons.

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F

F

A ratio of variances, calculated from a sample of data and used to provide information about a whole dataset. For example, statistic F may be used to provide estimates of variance, or differences, in a population, based on observations from two or more random samples.
 

F statistic

A ratio of variances, calculated from a sample of data and used to provide information about a whole dataset. For example, statistic F may be used to provide estimates of variance, or differences, in a population, based on observations from two or more random samples.
 

F test

A statistical test for determining the probability that the variances of two different samples are the same. The F test uses a statistic known as statistic F to test statistical hypotheses about the variances of distributions from which samples have been drawn.
 

fabric

In Survey Analyst - Cadastral Editor, a network of connected parcels. Parcels are represented by parcel line features, parcel point features, and parcel polygon features, referred to in aggregate as parcel features. Parcel topology in the cadastral fabric is stored explicitly through shared or common parcel point features.
 

face

A planar surface of a geometric shape, bounded by edges.
 

facility

In ArcGIS Network Analyst, a network location used in closest facility and service area analyses.
 

false easting

The linear value added to all x-coordinates of a map projection so that none of the values in the geographic region being mapped are negative.
 

false northing

The linear value added to all y-coordinates of a map projection so that none of the values in the geographic region being mapped are negative.
 

feature

A representation of a real-world object on a map.
 

feature attribute table

A database or tabular file containing information about a set of geographic features, usually arranged so that each row represents a feature and each column represents one feature attribute. In raster datasets, each row of an attribute table corresponds to a certain zone of cells having the same value. In a GIS, attribute tables are often joined or related to spatial data layers, and the attribute values they contain can be used to find, query, and symbolize features or raster cells.
 

feature class

In ArcGIS, a collection of geographic features with the same geometry type (such as point, line, or polygon), the same attributes, and the same spatial reference. Feature classes can be stored in geodatabases, shapefiles, coverages, or other data formats. Feature classes allow homogeneous features to be grouped into a single unit for data storage purposes. For example, highways, primary roads, and secondary roads can be grouped into a line feature class named "roads." In a geodatabase, feature classes can also store annotation and dimensions.
 

feature code

In Survey Analyst for field measurements, a block of text included in data collector file format, used to describe features surveyed in the field.
 

feature data

Data that represents geographic features as geometric shapes.
 

feature dataset

In ArcGIS, a collection of feature classes stored together that share the same spatial reference; that is, they share a coordinate system, and their features fall within a common geographic area. Feature classes with different geometry types may be stored in a feature dataset.
 

feature displacement

The movement of features that would otherwise overprint or conflict with other features. For example, if a river, a road, and a railway run through a narrow valley, it is necessary, at some scales, to displace at least one of the features that represent them on the map to keep their symbols distinct.
 

feature extraction

In image processing, a method of pattern recognition in which patterns within an image are measured and then classified as features based on those measurements.
 

feature layer

A layer that references a set of feature data. Feature data represents geographic entities as points, lines, and polygons.
 

feature server

A public ArcIMS virtual server for feature services.
 

feature service

A service that uses the ArcIMS spatial server feature streaming capabilities. The server bundles data and streams it to the requesting client. Since more of the processing is done in the Java applet, requests are sent to an ArcIMS spatial server only when additional data is needed.
 

feature streaming

The process of delivering vector feature data defined for a service that uses the feature server component. On the client side, feature streaming allows you to access a published map and then add feature data for overlays, sharing, making EditNotes, and performing analysis. Feature streaming functionality minimizes the need for multiple server requests.
 

feature table

A table in an ArcSDE geodatabase that stores geometric shapes for each feature. Feature tables are used in geodatabases that store data as a binary data type, such as SQL Server geodatabases. They are related to the business table of a feature class through the feature ID. In the database, feature table names are prefaced with an f and are stored in the schema of the user who owns the feature class.
 

feature weight

In ArcMap, a ranking system that indicates whether features from a given feature class may be covered by a label in cases where the label cannot be placed in free space. Feature classes with lower weights will tend to have labels placed over their features before feature classes with higher weights. Polygon feature classes have two types of weights: boundary weights and interior weights.
 

feature-linked annotation

Annotation that is stored in the geodatabase with links to features through a geodatabase relationship class. Feature-linked annotation reflects the current state of features in the geodatabase: it is automatically updated when features are moved, edited, or deleted.
 

Federal Geographic Data Committee

An organization established by the United States Federal Office of Management and Budget responsible for coordinating the development, use, sharing, and dissemination of surveying, mapping, and related spatial data. The committee is comprised of representatives from federal and state government agencies, academia, and the private sector. The FGDC defines spatial data metadata standards for the United States in its Content Standard for Digital Geospatial Metadata and manages the development of the National Spatial Data Infrastructure (NSDI).
 

FGDC

Acronym for Federal Geographic Data Committee. An organization established by the United States Federal Office of Management and Budget responsible for coordinating the development, use, sharing, and dissemination of surveying, mapping, and related spatial data. The committee is comprised of representatives from federal and state government agencies, academia, and the private sector. The FGDC defines spatial data metadata standards for the United States in its Content Standard for Digital Geospatial Metadata and manages the development of the National Spatial Data Infrastructure (NSDI).
 

FGDC Clearinghouse

An Internet server that hosts a collection of metadata and data maintained and stored on a computer server by a data provider. An NSDI Clearinghouse Node provides information about geographic data within the data provider's areas of responsibility. Nodes must host FGDC-compliant metadata and data and use a common access protocol.
 

FGDC standard

A publication authored by the FGDC that specifies the information content of metadata for digital geospatial datasets. The purpose of the standard is to provide a common set of terminology and definitions for concepts related to the metadata. All U.S. government agencies (federal, state, and local) that receive federal funds to create metadata must follow this standard.
 

FID

In ArcGIS, a system-managed value that uniquely identifies a record or feature.
 

field

A column in a table that stores the values for a single attribute.
 

field mapping

In geoprocessing, defining the field structure and content for an output dataset.
 

field precision

The number of digits that can be stored in a field in a table.
 

field scale

The number of decimal places for float or double-type geodatabase table fields.
 

field view

A philosophical view of geographic space in which space is completely filled by occurrences of phenomena, and in which phenomena are described by a range of values on a numeric scale. In this view, every spatial location is something, even if it is the zero value of a phenomenon.
 

file

A collection of uniquely named information stored on a drive, disk, or tape. A file generally resides within a directory.
 

file geodatabase

A geodatabase stored as a folder of files. A file geodatabase can be used simultaneously by several users, but only one user at a time can edit the same data.
 

file name

The name that distinguishes a file from all other files in a particular directory. It can refer to the name of the file by itself (harold), the name plus the file extension (harold.shp), or the whole path of a file up to and including the file name extension (C:\mygisdata\shapefiles\harold.shp).
 

file name extension

The abbreviation following the final period in a file name that indicates the file's format, such as .shp, .zip, or .tif. File name extensions are usually one to four letters long.
 

File Transfer Protocol

A protocol that allows the transmission of files between computers over a network.
 

fill

The interior of a polygon; the area inside the perimeter.
 

fill symbol

A color or pattern used to fill polygons on a map.
 

fillet

A segment of a circle used to connect two intersecting lines. Fillets are used to create smoothly curving connections between lines, such as pavement edges at street intersections or rounded corners on parcel features.
 

filter

On a raster, an analysis boundary or processing window within which cell values affect calculations and outside which they do not. Filters are used mainly in cell-based analysis where the value of a center cell is changed to the mean, the sum, or some other function of all cell values inside the filter. A filter moves systematically across a raster until each cell has been processed. Filters can be of various shapes and sizes, but are most commonly three-cell by three-cell squares.
 

Find Addresses

An ArcWeb tool for ArcGIS that enables users to input a street address and receive a candidate list of matched locations for display on a map.
 

Find Places

An ArcWeb tool for ArcGIS that allows users to search for place-names and receive a candidate list of place-names and associated coordinates for display on a map.
 

Find Points of Interest

An ArcWeb tool for ArcGIS that enables users to define spatial or attribute queries and display the results on a map.
 

Find Route

An ArcWeb tool for ArcGIS that lets users generate multipoint driving directions between user-defined locations. The Find Route tool determines the shortest or the quickest path between locations and creates a map of the travel route and a list of travel directions.
 

Find Similar analysis

A process that seeks out new market areas based on the characteristics of an existing market area.
 

first normal form

The first level of guidelines for designing table and data structures in a relational database. The first normal form guideline recommends creating a unique key for every row in a database table, eliminating duplicate columns from a table, and creating separate tables to contain related data. A database that follows these guidelines is said to be in first normal form.
 

fitness for use

The degree to which a dataset is suitable for a particular application or purpose, encompassing factors such as data quality, scale, interoperability, cost, data format, and so on.
 

fix

A single position obtained by surveying, GPS, or astronomical measurements, usually given with altitude, time, date, and latitude-longitude or grid position.
 

fixed reference point

In Survey Analyst for field measurements, a survey point used as an input to a computation. The coordinates are not updated by the computation.
 

fixed use

In software licensing, a software product that can be used on only one machine.
 

fixed-time data

In ArcGIS Tracking Analyst, stored temporal data that can be viewed in past, future, and past-and-future time windows. This data is stored in a shapefile or as a feature class in a geodatabase.
 

flag

A marker that identifies or calls attention to something, indicating importance or the need for further attention.
 

Flash

A browser-independent, vector graphic technology for creating interactive Web sites with video, graphics, and animation. Browsers need plug-ins for Flash animations.
 

flatbed scanner

A type of scanner with a flat, clear surface on which a map or image remains stationary while a sensor beam moves across it and captures a digital image.
 

flattening

A measure of how much an oblate spheroid differs from a sphere. The flattening equals the ratio of the semimajor axis minus the semiminor axis to the semimajor axis.
 

Flex

A set of tools that allows developers to create cross-platform, browser-independent Web applications using a standards-based programming language. Created by Macromedia in 2004 and now developed by Adobe, the Flex family of products includes Flex SDK, Flex Builder, Flex Data Services, and Flex Charting.
 

floating layer

A layer in ArcGlobe that has been categorized to float independently above or below the globe surface.
 

floating point

A type of numeric field for storing real numbers with a decimal point. The decimal point can be in any position in the field and, thus, may "float" from one location to another for different values stored in the field. For example, a floating-point field can store the numbers 23.632, 0.000087, and -96432.15.
 

floating use

Floating software products that are administered by a license manager. A central license manager (installed anywhere on a network) allows users to install the floating products on any number of machines. The number of seats or licenses purchased determines the number of users who can run the applications simultaneously.
 

flow direction

The route or course followed by commodities proceeding through edge elements in a network.
 

flow map

A map that uses line symbols of variable thickness to show the proportion of traffic or flow within a network.
 

focal analysis

The computation of an output raster where the output value at each cell location is a function of the value at that cell location and the values of the cells within a specified neighborhood around the cell.
 

focal functions

The computation of an output raster where the output value at each cell location is a function of the value at that cell location and the values of the cells within a specified neighborhood around the cell.
 

focus field

In Survey Analyst for field measurements, the field that is the current target for data entry.
 

folder

A location on a disk containing a set of files, other folders, or both.
 

folder connection

In ArcCatalog, a top-level item in the Catalog tree that provides quick access to geographic data stored on local disks (including CD-ROMs) or shared on a network. Folder connections may provide access to individual folders.
 

follow feature mode

In ArcGIS, a method for placing geodatabase annotation relative to a line or polygon feature. For example, text next to a river may be dragged along it so that the text curves like the river.
 

font

A single typeface or a set of related patterns representing characters or symbols at one size.
 

footprint

In ArcGIS Image Server, the extent (often rectangular) of each raster dataset in the image service definition. The footprint is stored as a polygon shapefile within the image service definition.
 

force concentration

In MOLE, a component of a map display that shows where force units are located so that the map reader can see where forces are the strongest and weakest.
 

force element

In MOLE, a type of graphic that represents a military unit (such as Company A, 1st Battalion of the 135th Infantry), equipment, or installation (such as a hospital or radar site). Force elements are also known as force units or military units.
 

foreground

In a scene or display, the area that appears to be closest to an observer.
 

foreign key

An attribute or set of attributes in one table that match the primary key attributes in another table. Foreign keys and primary keys are used to join tables in a database.
 

form lines

Lines on a map that approximate the shape of terrain in lieu of actual contours. Form lines do not refer to a true datum and do not necessarily use regular intervals.
 

format

In computing, the structure and organization of digital information.
 

formatted text tag

Tags used with text in ArcGIS that allow formatting to be modified for a portion of a text string. This allows the creation of mixed-format text where, for example, one word in a sentence is underlined. Text formatting tags adhere to XML syntax rules and can be used most places where both a text string and a text symbol can be specified. The tags are most commonly used with labels, annotation, and graphic text.
 

fractal

A geometric pattern that repeats itself, at least roughly, at ever smaller scales to produce self-similar, irregular shapes and surfaces that cannot be represented using classical geometry. If a fractal curve of infinite length serves as the boundary of a plane region, the region itself will be finite. Fractals can be used to model complex natural shapes such as clouds and coastlines.
 

frame

In MOLE, the geometric border of a graphic that indicates the affiliation, battle dimension, and status of the war fighting element that the MOLE graphic represents.
 

framework

The existing ArcObjects components that comprise the ArcGIS system.
 

free network adjustment

In Survey Analyst for field measurements, one of two phases involved when performing a least squares adjustment for a measurement network. The free network adjustment phase examines the overall geometry of the network by processing only the measurements and using the reference points only for position scale and orientation of the network. The emphasis is on testing the quality of the measurements rather than computing the coordinates.
 

free representation

In ArcGIS, the representation of a single feature that has been disconnected from its representation rule to create an independent rule whose structure can be changed, allowing full freedom of display. Geometric effects within the rule can be converted so that their results become static parts of the feature representation.
 

freeze

To fix a column in place in a table for better viewing of the table's contents. A frozen column will stay in place while the other columns scroll normally.
 

frequency

The number of oscillations per unit of time in a wave of energy, or the number of wavelengths that pass a point in a given amount of time.
 

from-node

Of an arc's two endpoints, the first one digitized. From- and to-nodes give an arc left and right sides and, therefore, direction.
 

FTP

Acronym for File Transfer Protocol. A protocol that allows the transmission of files between computers over a network.
 

full cache

In ArcGlobe, a layer cache saved on disk that contains complete levels of details for the entire layer.
 

function

An operation. In GIS, functions include data input, editing, and management; data query, analysis, and visualization; and output operations.
 

functional surface

In 3D Analyst, a surface that stores a single z-value for any given x,y location.
 

fuzzy boundary

A boundary that has a vague or indeterminate location, or that is a gradual transition between two zones.
 

fuzzy classification

Any method for classifying data that allows attributes to apply to objects by membership values, so that an object may be considered a partial member of a class. Class membership is usually defined on a continuous scale from zero to one, where zero is nonmembership and one is full membership. Fuzzy classification may also be applied to geographic objects themselves, so that an object's boundary is treated as a gradated area rather than an exact line. In GIS, fuzzy classification has been used in the analysis of soil, vegetation, and other phenomena that tend to change gradually in their physical composition and for which attributes are often partly qualitative in nature.
 

fuzzy set

In mathematics, a collection of elements that belong together based on specified criteria, so that elements with partial or uncertain degrees of membership may be included in the collection.
 

fuzzy tolerance

The distance within which coordinates of nearby features are adjusted to coincide with each other when topology is being constructed or polygon overlay is performed. Nodes and vertices within the fuzzy tolerance are merged into a single coordinate location. Fuzzy tolerance is a very small distance, usually from 1/1,000,000 to 1/10,000 times the width of the coverage extent, and is generally used to correct inexact intersections.

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G

Gantt chart

A project management graph that displays tasks on a schedule, often used to plan and track projects. The Gantt chart was developed by the American mechanical engineer and management consultant Henry Laurence Gantt. 
 

gateway

An OpenLS ArcWeb service that determines the location of wireless devices.
 

Gateway Service

An OpenLS ArcWeb service that determines the location of wireless devices.
 

Gaussian distribution

A theoretical frequency distribution of a dataset in which the distribution of values can be graphically represented as a symmetrical bell curve. Normal distributions are typically characterized by a clustering of values near the mean, with few values departing radically from the mean. There are as many values on the left side of the curve as on the right, so the mean and median values for the distribution are the same. Sixty-eight percent of the values are plus or minus one standard deviation from the mean; 95 percent of the values are plus or minus two standard deviations; and 99 percent of the values are plus or minus three standard deviations.
 

Gauss-Kruger projection

A projected coordinate system that uses the transverse Mercator projection to divide the world into standard zones 6 degrees wide. Used mainly in Europe and Asia, the Gauss-Krüger coordinate system is similar to the universal transverse Mercator coordinate system. The Gauss-Krüger projection is named for the German mathematician and scientist Karl Friedrich Gauss and the German geodesist and mathematician Johann Heinrich Louis Krüger.
 

gazetteer

A list of geographic place-names and their coordinates. Entries may include other information as well, such as area, population, or cultural statistics. Atlases often include gazetteers, which are used as indexes to their maps. Well-known digital gazetteers include the U.S. Geological Survey Geographic Names Information System (GNIS) and the Alexandria Digital Library Gazetteer.
 

GBF/DIME

Acronym for Geographic Base Files/Dual Independent Map Encoding. Vector geographic base files made for the 1970 and 1980 U.S. censuses, containing address ranges, ZIP Codes, and the coordinates of street segments and intersections for most metropolitan areas in the United States. TIGER files replaced DIME files for the 1990 and subsequent censuses.
 

GDB

A database or file structure used primarily to store, query, and manipulate spatial data. Geodatabases store geometry, a spatial reference system, attributes, and behavioral rules for data. Various types of geographic datasets can be collected within a geodatabase, including feature classes, attribute tables, raster datasets, network datasets, topologies, and many others. Geodatabases can be stored in IBM DB2, IBM Informix, Oracle, Microsoft Access, Microsoft SQL Server, and PostgreSQL relational database management systems, or in a system of files, such as a file geodatabase.
 

GDI

Acronym for Graphical Device Interface. A standard for displaying and transmitting text and graphical objects output devices, such as monitors and printers. GDI generally refers to the Windows GDI API.
 

generalization

The abstraction, reduction, and simplification of features for change of scale or resolution.
 

genetic algorithm

A search algorithm inspired by genetics and Darwin's theory of natural selection. The algorithm goes through an iterative process of applying genetic operators, such as reproduction, mutation, and crossover, to a collection of data over several stages. At each stage the fitness of the results is evaluated and the best of the results population is retained, until the results present an optimal solution.
 

geocentric

Measured from the earth or the earth's center.
 

geocentric coordinate system

A three-dimensional, earth-centered reference system in which locations are identified by their x-, y-, and z-values. The x-axis is in the equatorial plane and intersects the prime meridian (usually Greenwich). The y-axis is also in the equatorial plane; it lies at right angles to the x-axis and intersects the 90-degree meridian. The z-axis coincides with the polar axis and is positive toward the north pole. The origin is located at the center of the sphere or spheroid.
 

geocentric datum

A horizontal geodetic datum based on an ellipsoid that has its origin at the earth's center of mass. Examples are the World Geodetic System of 1984, the North American Datum of 1983, and the Geodetic Datum of Australia of 1994. The first uses the WGS84 ellipsoid; the latter two use the GRS80 ellipsoid. Geocentric datums are more compatible with satellite positioning systems, such as GPS, than are local datums.
 

geocentric latitude

The angle between the equatorial plane and a line from a point on the surface to the center of the sphere or spheroid. On a sphere, all lines of latitude are geocentric. Latitude generally refers to geodetic latitude.
 

geocentric longitude

The angle between the prime meridian and a line drawn from a point on the surface to the center of a sphere or spheroid. For an ellipsoid of revolution (such as the earth), geocentric longitude is the same as geodetic longitude.
 

geocloud

The term “cloud” represents the internet/web. Geocloud /Geocloud computing therefore is the ability for consumers, developers and applications to access computing resources from the cloud. These geographically aware/ spatial computing resources could be owned and operated by some third party provider – either for free or for a fee.
 

geocode

To assign a street address to a location.
 

geocoded feature class

A feature class created by batch geocoding.
 

GeocodeServer

An ArcGIS Server software component that provides programmatic access to an address locator and performs single and batch address matching. It is designed for use in building Web services and Web applications using ArcGIS Server.
 

geocoding

A GIS operation for converting street addresses into spatial data that can be displayed as features on a map, usually by referencing address information from a street segment data layer.
 

geocoding engine

An entity in the geocoding framework that drives the geocoding process.
 

geocoding index

An index on reference data used by an address locator to search for matching records in the reference data. A geocoding index is either a file or a database table containing index attributes used by the address locator.
 

geocoding platform

A conceptual entity of the geocoding framework that combines the interaction of the ArcGIS interface with the input parameters set in the address locator and the processes of the geocoding engine.
 

geocoding process

The steps involved in translating an address entry, searching for the address in the reference data embedded in an address locator, and delivering the best candidate or candidates. These steps include parsing the address, standardizing abbreviated values, assigning each address element to a category known as a match key, indexing the needed categories, searching the reference data, assigning a score to each potential candidate, filtering the list of candidates based on the minimum match score, and delivering the best match. The process requires reference files, input address records, address locators, and software.
 

geocoding reference data

Data that a geocoding service uses to determine the geometric representations for locations.
 

geocoding rule base

A collection of files that directs the geocoding engine in how to standardize address data and match it to the related location in the reference data. Each address locator style uses a specific rule base designed for that style.
 

geocoding service

In ArcGIS 8.3 and previous versions, an object that defines the process for translating nonspatial descriptions of places, such as street addresses, into spatial data that can be displayed as features on a map. A geocoding service defines the path to the reference data source and the file of nonspatial data, algorithms for standardizing addresses and matching them to the reference data, and parameters for reading address data, matching address data to the reference data, and creating output. In ArcGIS 9, a geocoding service is called an address locator.
 

geocoding style

A template on which a geocoding service is built. Each template is designed to accommodate a specific format of address and reference data, and geocoding parameters. Geocoding style template files have a .lot file extension.
 

geocomputation

The application of computer technology to spatial problems, including problems of collecting, storing, visualizing, and analyzing spatial data, and of modeling spatial system dynamics.
 

geodata

Information describing the location and attributes of things, including their shapes and representation. Geographic data is the composite of spatial data and attribute data.
 

geodatabase

A database or file structure used primarily to store, query, and manipulate spatial data. Geodatabases store geometry, a spatial reference system, attributes, and behavioral rules for data. Various types of geographic datasets can be collected within a geodatabase, including feature classes, attribute tables, raster datasets, network datasets, topologies, and many others. Geodatabases can be stored in IBM DB2, IBM Informix, Oracle, Microsoft Access, Microsoft SQL Server, and PostgreSQL relational database management systems, or in a system of files, such as a file geodatabase.
 

geodatabase data model

The schema for the various geographic datasets and tables in an instance of a geodatabase. The schema defines the GIS objects, rules, and relationships used to add GIS behavior and integrity to the datasets in a collection. 
 

geodatabase feature dataset

In a geodatabase, a collection of feature classes stored together so they can participate in topological relationships with one another. All the feature classes in a feature dataset must share the same spatial reference; that is, they must have the same coordinate system and their features must fall within a common geographic area. Feature classes with different geometry types may be stored in a feature dataset. In ArcGIS, feature classes that participate in a geometric network must be placed in a feature dataset. 
 

geodatabase replication

In ArcGIS, a method of distributing data across two or more geodatabases in order to synchronize data changes. An entire geodatabase or a subset of a geodatabase can be replicated. There are three types of geodatabase replication: two-way replication, one-way replication, and check-out replication. 
 

GeoDataServer

In ArcGIS, a coarse-grained object that represents a geodatabase. It allows software users to perform replication operations, data extraction and database query operations on a geodatabase over the WAN using ArcGIS Server. Application developers can also use the GeoDataServer with geodatabase connections made over the LAN. 
 

geodataset

Any organized collection of data in a geodatabase with a common theme. 
 

geodesic

The shortest distance between two points on the surface of a spheroid. Any two points along a meridian form a geodesic. 
 

geodesy

The science of measuring and representing the shape and size of the earth, and the study of its gravitational and magnetic fields. 
 

geodetic datum

A datum that is the basis for calculating positions on the earth's surface or heights above or below the earth's surface. 
 

geodetic latitude

The angle that a line drawn perpendicular to the surface through a point on a spheroid makes with the equatorial plane. 
 

geodetic longitude

The angle between the plane of the meridian that passes through a point on the surface of the spheroid and the plane of a prime meridian, usually the Greenwich meridian. 
 

Geodetic Reference System of 1980

The standard measurements of the earth's shape and size adopted by the International Union of Geodesy and Geophysics in 1979. 
 

geodetic survey

A survey that takes the shape and size of the earth into account, used to precisely locate horizontal and vertical positions suitable for controlling other surveys. 
 

geodetic transformation

A systematic conversion of the latitude-longitude values for a set of points from one geographic coordinate system to equivalent values in another geographic coordinate system. Depending on the geographic coordinate systems involved, the transformation can be accomplished in various ways. Typically, equations are used to model the position and orientation of the "from" and "to" geographic coordinate systems in three-dimensional coordinate space; the transformation parameters may include translation, rotation, and scaling. Other methods, including one used in transformations between NAD 1927 and NAD 1983, use files in which the differences between the two geographic coordinate systems are given for a set of coordinates; the values of other points are interpolated from these. 
 

geofence

A designated boundary around a geometry that, if crossed, initiates a notification. Geofences are often used in real-time route Web applications. 
 

geographic

Of or relating to the earth. 
 

geographic constraint

The minimum bounding rectangle (xmin, ymin and xmax, ymax) defined by coordinate pairs of a data source. All coordinates for the data source fall within this boundary. 
 

geographic coordinate system

A reference system that uses latitude and longitude to define the locations of points on the surface of a sphere or spheroid. A geographic coordinate system definition includes a datum, prime meridian, and angular unit. 
 

geographic coordinates

A measurement of a location on the earth's surface expressed in degrees of latitude and longitude. 
 

geographic data

Information describing the location and attributes of things, including their shapes and representation. Geographic data is the composite of spatial data and attribute data. 
 

geographic database

A database or file structure used primarily to store, query, and manipulate spatial data. Geodatabases store geometry, a spatial reference system, attributes, and behavioral rules for data. Various types of geographic datasets can be collected within a geodatabase, including feature classes, attribute tables, raster datasets, network datasets, topologies, and many others. Geodatabases can be stored in IBM DB2, IBM Informix, Oracle, Microsoft Access, Microsoft SQL Server, and PostgreSQL relational database management systems, or in a system of files, such as a file geodatabase. 
 

geographic information science

The field of research that studies the theory and concepts that underpin GIS. It seeks to establish a theoretical basis for the technology and use of GIS, study how concepts from cognitive science and information science might apply to GIS, and investigate how GIS interacts with society. 
 

geographic information system

An integrated collection of computer software and data used to view and manage information about geographic places, analyze spatial relationships, and model spatial processes. A GIS provides a framework for gathering and organizing spatial data and related information so that it can be displayed and analyzed. 
 

geographic north

The direction from any point on the earth's surface to the geographic north pole. 
 

geographic primitive

In MOLE, the most elementary part of a graphic. Icon, frame, and fill are examples of components that make up MOLE graphics. 
 

geographic projection

The coordinate system used for displaying geographic data. Examples include the data frame in ArcMap and the view in ArcView GIS. 
 

geographic transformation

A systematic conversion of the latitude-longitude values for a set of points from one geographic coordinate system to equivalent values in another geographic coordinate system. Depending on the geographic coordinate systems involved, the transformation can be accomplished in various ways. Typically, equations are used to model the position and orientation of the "from" and "to" geographic coordinate systems in three-dimensional coordinate space; the transformation parameters may include translation, rotation, and scaling. Other methods, including one used in transformations between NAD 1927 and NAD 1983, use files in which the differences between the two geographic coordinate systems are given for a set of coordinates; the values of other points are interpolated from these. 
 

geography

The study of the earth's surface, encompassing the description and distribution of the various physical, biological, economic, and cultural features found on the earth and the interaction between those features. 
 

geography level

A division of statistical geographic data, such as country, province, postal code, tract, or block group. 
 

Geography Markup Language

An OpenGIS Implementation Specification designed to store and transport geographic information. GML is a profile (encoding) of XML. 
 

geoid

A hypothetical surface representing the form the earth's oceans would take if there were no land and the water were free to respond to the earth's gravitational and centrifugal forces. The resulting geoid is irregular and varies from a perfect sphere by as much as 75 meters above and 100 meters below its surface. 
 

geoid height

The height of the geoid above the ellipsoid. 
 

geoid-ellipsoid separation

The distance from the surface of an ellipsoid to the surface of the geoid, measured along a line perpendicular to the ellipsoid. The separation is positive if the geoid lies above the ellipsoid, negative if it lies below. 
 

geolocation

The process of creating geographic features from tabular data by matching the tabular data to a spatial location. An example of geolocation is creating point features from a table of x,y coordinate. 
 

geometric coincidence

The distance within which features in a geometric network are deemed to be coincident and, therefore, connected. 
 

geometric correction

The correction of errors in remotely sensed data, such as those caused by satellites or aircraft not staying at a constant altitude or by sensors deviating from the primary focus plane. Images are often compared to ground control points on accurate basemaps and resampled, so that exact locations and appropriate pixel values can be calculated. 
 

geometric dilution of precision

An indicator of satellite geometry for a constellation of satellites used to determine a position. Positions with a lower DOP value generally constitute better measurement results than those with higher DOP. Factors determining the total GDOP (geometric DOP) for a set of satellites include PDOP (positional DOP), HDOP (horizontal DOP), VDOP (vertical DOP), and TDOP (time DOP). 
 

geometric effect

In ArcGIS, a dynamic process that can be applied within a representation rule to dynamically alter the geometry of features before they are drawn. Geometric effects can act on a single symbol layer, or on all symbol layers in a representation rule, and can be chained together to create cumulative effects. 
 

geometric element

One of the most basic parts or components of a geometric figure: that is, a surface, shape, point, line, angle, or solid. 
 

geometric network

Edge and junction features that represent a linear network, such as a utility or hydrologic system, in which the connectivity of features is based on their geometric coincidence. A geometric network does not contain information about the connectivity of features; this information is stored within a logical network. Geometric networks are typically used to model directed flow systems. 
 

geometric transformation

The process of rectifying a raster dataset to map coordinates or converting a raster dataset from one coordinate system to another. 
 

geometry

The measures and properties of points, lines, and surfaces. In a GIS, geometry is used to represent the spatial component of geographic features. 
 

GeoMobility Server

An OpenLS platform for wireless Web services defined by the Open Geospatial Consortium. 
 

geomorphology

The study of the nature and origin of landforms, including relationships to underlying structures and processes of formation. 
 

geoprocessing

A GIS operation used to manipulate GIS data. A typical geoprocessing operation takes an input dataset, performs an operation on that dataset, and returns the result of the operation as an output dataset. Common geoprocessing operations include geographic feature overlay, feature selection and analysis, topology processing, raster processing, and data conversion. Geoprocessing allows for definition, management, and analysis of information used to form decisions. 
 

geoprocessing server

A computer in a network that is used to handle geoprocessing tasks. Geoprocessing servers may use UNIX or Windows platforms, and include a utility to schedule remote processing. 
 

geoprocessing settings

Any settings that affect working with or running tools. Geoprocessing settings include the state of the ArcToolbox window, the state of the Environment Settings dialog box, and variables that have been created at the command line. In ArcMap, geoprocessing settings are saved with a map document. In ArcCatalog, geoprocessing settings are persisted with the application. 
 

geoprocessing tool

An ArcGIS tool that can create or modify spatial data, including analysis functions (overlay, buffer, slope), data management functions (add field, copy, rename), or data conversion functions. 
 

GEOPUB30.DLL

An ArcView Geocoding Windows dynamic link library (DLL) for use on ArcView 3.x. It exposes additional geocoding requests by making them public (rather than private), Avenue scripts-callable requests. 
 

georectification

The digital alignment of a satellite or aerial image with a map of the same area. In georectification, a number of corresponding control points, such as street intersections, are marked on both the image and the map. These locations become reference points in the subsequent processing of the image. 
 

georeferencing

Aligning geographic data to a known coordinate system so it can be viewed, queried, and analyzed with other geographic data. Georeferencing may involve shifting, rotating, scaling, skewing, and in some cases warping, rubber sheeting, or orthorectifying the data. 
 

georelational data model

A geographic data model that represents geographic features as an interrelated set of spatial and attribute data. The georelational model is the fundamental data model used in coverages. 
 

GeoRSS

Acronym for Geographically Encoded Objects for RSS feeds. Metadata for RSS documents that describes the location of Web content. 
 

geospatial data clearinghouse

A community of digital spatial data providers that maintain NSDI Clearinghouse Nodes as part of the U.S. National Spatial Data Infrastructure. 
 

geospatial technology

A set of technological approaches, such as GIS, photogrammetry, and remote sensing, for acquiring and manipulating geographic data. 
 

geospecific model

A model used to represent a real-world feature. For example, a geospecific model for the White House would look exactly like the White House and be used to represent the White House on a map of Washington, D.C. 
 

geostationary

Positioned in an orbit above the earth's equator with an angular velocity the same as that of the earth and an inclination and eccentricity approaching zero. A geostationary satellite will orbit as fast as the earth rotates on its axis, so that it remains effectively stationary above a point on the equator. A geostationary satellite is geosynchronous, but geosynchronous satellites are not necessarily geostationary. 
 

geostatistical layer file

A layer file created by the ArcGIS Geostatistical Analyst extension. It can be exported to ESRI GRID for further geoprocessing. 
 

geostatistics

A class of statistics used to analyze and predict the values associated with spatial or spatio-temporal phenomena. Geostatistics provides a means of exploring spatial data and generating continuous surfaces from selected sampled data points. 
 

geosurvey engine

The software module in Survey Analyst - Cadastral Editor that manages the interaction between cadastral fabric jobs and the cadastral fabric. 
 

geosynchronous

Positioned in an orbit moving west to east with an orbital period equal to the earth's rotational period. If a satellite is in a geosynchronous orbit that is circular and lies in the equatorial plane, it is geostationary because it remains over one point on the equator. If not, the satellite appears to make a figure eight once a day between the latitudes that correspond to its angle of inclination over the equator. 
 

geotypical model

A symbolic representation for a class of map features, such as government buildings. For example, on a map of the United States, a white building with a dome on top could be used as a geotypical model for all state capitols. 
 

Get Report

An ArcWeb tool for ArcGIS that enables users to determine characteristics for a specified location and generate a report. 
 

GIF

Acronym for Graphic Interchange Format. A low-resolution file format for image files, commonly used on the Internet. It is well-suited for images with sharp edges and reduced numbers of colors. 
 

giomgr

In ArcSDE, a process that listens for client requests to connect to the database. When it receives such a request, it creates a connection by launching a gsrvr process dedicated to that client. The giomgr process is not used if the client makes a direct connection to the ArcSDE geodatabase. 
 

GIS

Acronym for geographic information system. An integrated collection of computer software and data used to view and manage information about geographic places, analyze spatial relationships, and model spatial processes. A GIS provides a framework for gathering and organizing spatial data and related information so that it can be displayed and analyzed. 
 

GIS coordinate

In Survey Analyst for field measurements, the single coordinate for a survey point that is the best overall representation for that survey point's location, defined by one or more projects. Feature geometry is always linked to the GIS coordinate. 
 

GIS Data ReViewer

An application used to manage data quality control, visually check data and run batch checks for attribute and geometry defects. Defects are recorded in an error table that can be used to resolve errors and verify corrections.
 

GIS server

The components of ArcGIS Server that host and run services. A GIS server consists of a server object manager and one or more server object containers.
 

GIScience

Abbreviation for geographic information science. The field of research that studies the theory and concepts that underpin GIS. It seeks to establish a theoretical basis for the technology and use of GIS, study how concepts from cognitive science and information science might apply to GIS, and investigate how GIS interacts with society.
 

global analysis

The computation of an output raster where the output value at each cell location may be a function of all the cells in the input raster.
 

Global Check method

In Survey Analyst for field measurements, one of two ways to apply the Coordinate Out of Tolerance command. The Global Check method searches for coordinates out of tolerance within the whole survey dataset.
 

global functions

The computation of an output raster where the output value at each cell location may be a function of all the cells in the input raster.
 

global mode

A navigation mode in ArcGlobe during which the camera target is always at the center of the globe.
 

Global Navigation Satellite System

The Russian counterpart of the United States Global Positioning System.
 

global polynomial interpolation

In ArcGIS Geostatistical Analyst, a deterministic interpolation method. The interpolated surface is not required to conform to the sample data points, and the method does not have standard errors associated with it.
 

Global Positioning System

A system of radio-emitting and -receiving satellites used for determining positions on the earth. The orbiting satellites transmit signals that allow a GPS receiver anywhere on earth to calculate its own location through trilateration. Developed and operated by the U.S. Department of Defense, the system is used in navigation, mapping, surveying, and other applications in which precise positioning is necessary.
 

global spatial data infrastructure

A global framework of technologies, policies, standards, and human resources necessary to acquire, process, store, distribute, and improve the use of geospatial data across multiple countries and organizations.
 

GlobalID

A field of type UUID (Universal Unique Identifier) in which values are automatically assigned by the geodatabase when a row is created. The GlobalID field is necessary for maintaining object uniqueness across replicas. All feature classes and tables participating in one-way or two-way replication must contain the GlobalID field. This field is not editable and is automatically populated when it is added for existing data.
 

globally unique identifier

A string used to uniquely identify an interface, class, type library, component category, or record.
 

globe

A sphere on which a map of the earth or a celestial body is represented. Since the earth's natural shape is similar to a sphere, globes distort the earth's features far less than flat maps.
 

globe document

A disk-based representation of the globe view or views contained in ArcGlobe. Globe documents have a .3dd extension.
 

globe properties

In ArcGlobe, properties that can be set for a globe document. These include vertical exaggeration, background color, or sun position.
 

globe terrain

In ArcGlobe, a globe surface with base heights supplied from an elevation layer.
 

globe view

In ArcGlobe, the display window in which a globe can be viewed.
 

GLONASS

Acronym for Global Navigation Satellite System. The Russian counterpart of the United States Global Positioning System.
 

Glue

A Java-based toolkit for accessing SOAP Web services. Glue is developed by webMethods.
 

glyph

The geometric shape of a character in a font.
 

GML

Acronym for Geography Markup Language. An OpenGIS Implementation Specification designed to store and transport geographic information. GML is a profile (encoding) of XML.
 

GMT

The time at the prime meridian, which runs through the Royal Observatory in Greenwich, England. From 1884 to 1928, Greenwich mean time was the official name (and is still the popular name) for universal time. It sometimes also refers to coordinated universal time.
 

gnomonic projection

A planar projection, tangent to the earth at one point, projected from the center of the globe. All great circles appear as straight lines on this projection, so that the shortest distance between two points is a straight line. The gnomonic projection is useful in navigation. The gnomonic projection was used by Thales of Miletus, an ancient Greek astronomer and philosopher, to chart the heavens. It is possibly the oldest map projection.
 

gon

A unit of angular measurement in which the angle of a full circle is 400 gradians and a right angle is 100 gradians. The common abbreviation for gradian is grad.
 

goodness of fit

In modeling, the degree to which a model predicts observed data; a measure of predictive power.
 

gore

A map, shaped like the area between a pair of parentheses, of an area that lies between two lines of longitude. A gore can be fitted to the surface of a globe with little distortion.
 

GPS

Acronym for Global Positioning System. A system of radio-emitting and -receiving satellites used for determining positions on the earth. The orbiting satellites transmit signals that allow a GPS receiver anywhere on earth to calculate its own location through trilateration. Developed and operated by the U.S. Department of Defense, the system is used in navigation, mapping, surveying, and other applications in which precise positioning is necessary.
 

grad

A unit of angular measurement in which the angle of a full circle is 400 gradians and a right angle is 100 gradians. The common abbreviation for gradian is grad.
 

gradian

A unit of angular measurement in which the angle of a full circle is 400 gradians and a right angle is 100 gradians. The common abbreviation for gradian is grad.
 

gradient

The ratio between vertical distance (rise) and horizontal distance (run), often expressed as a percentage. A 10-percent gradient rises 10 feet for every 100 feet of horizontal distance.
 

gradient of gravity

The direction of the maximum increase in gravity in a horizontal plane.
 

graduated color map

A map on which a range of colors indicates a progression of numeric values. For example, increases in population density might be represented by the increased saturation of a single color, or temperature differences by a sequence of colors from blue to red.
 

graduated symbol map

A map with symbols that change in size according to the value of the attribute they represent. For example, denser populations might be represented by larger dots, or larger rivers by thicker lines.
 

grain tolerance

In ArcInfo Workstation, a parameter controlling the number of vertices and the distance between them on lines that represent curves. The smaller the grain tolerance, the closer the vertices can be. Unlike densify tolerance, grain tolerance can affect the shape of curves.
 

granularity

The coarseness or resolution of data. Granularity describes the clarity and detail of data during its capture and visualization.
 

graph

A map used to plot a course for air or water navigation.
 

graphic

An image produced by and stored in a computer as data for display.
 

graphic component

In MOLE, the most elementary part of a graphic. Icon, frame, and fill are examples of components that make up MOLE graphics.
 

graphic text

Text added in ArcMap layout view that exists in page space and is stored in a map document. Graphic text does not move if the extent or scale is changed.
 

Graphical Device Interface

A standard for displaying and transmitting text and graphical objects output devices, such as monitors and printers. GDI generally refers to the Windows GDI API.
 

graphical user interface

A software display of program options that allows a user to choose commands by pointing to icons, dialog boxes, and lists of menu items on the screen, typically using a mouse. This contrasts with a command line interface in which control is accomplished via the exchange of strings of text.
 

graticule

A network of longitude and latitude lines on a map or chart that relates points on a map to their true locations on the earth.
 

graticule alignment of labels

A label positioning method in which labels are oriented along the graticule of the data frame. This is useful for maps of large areas, for cartographic or stylistic reasons.
 

gravimeter

A device used to measure small variations in the earth's gravitational field between two or more points.
 

gravimetric geodesy

The science of deducing the size and shape of the earth by measuring its gravitational field.
 

gravity model

A model that assumes that the influence of phenomena or populations on each other varies inversely with the distance between them.
 

gray scale

All the shades of gray from white to black.
 

great circle

Any circle or near circle produced by the intersection of the surface of a sphere and a flat plane that passes through the center of the sphere. The equator and all lines of longitude are great circles. Great circles are used in navigation, since the shortest path between any two points on the earth's surface lies on a great circle.
 

Greenwich mean time

The time at the prime meridian, which runs through the Royal Observatory in Greenwich, England. From 1884 to 1928, Greenwich mean time was the official name (and is still the popular name) for universal time. It sometimes also refers to coordinated universal time.
 

Greenwich meridian

The meridian adopted by international agreement in 1884 as the prime meridian, the 0-degree meridian from which all other longitudes are calculated. The Greenwich prime meridian runs through the Royal Observatory in Greenwich, England.
 

grid

In cartography, any network of parallel and perpendicular lines superimposed on a map and used for reference. These grids are usually referred to by the map projection or coordinate system they represent, such as universal transverse Mercator grid.
 

grid cell

The smallest unit of information in raster data, usually square in shape. In a map or GIS dataset, each cell represents a portion of the earth, such as a square meter or square mile, and usually has an attribute value associated with it, such as soil type or vegetation class.
 

grid meridian

In Survey Analyst for field measurements, any meridian that is parallel to the central meridian, used when computing points in planar rectangular coordinate systems of limited extent.
 

grid north

The direction north along the north-south grid lines of a map projection.
 

grid stack

A mechanism for storing multivariate raster data in ESRI software, consisting of an ordered set of spatially overlapping grids (referred to as layers) referenced by an INFO file or geodatabase. A stack is treated as a single entity for multivariate analysis. Cluster analysis, classification, and principal component analysis all work on the layers in a stack.
 

ground control

A system of points with known positions, elevations, or both, used as fixed references in georeferencing map features, aerial photographs, or remotely sensed images.
 

ground control point

An accurately surveyed coordinate location for a physical feature that can be identified on the ground. Control points are used in least-squares adjustments as the basis for improving the spatial accuracy of all other points to which they are connected.
 

ground receiving station

Communications equipment for receiving and transmitting signals to and from satellites such as Landsat.
 

ground truth

The accuracy of remotely sensed or mathematically calculated data based on data actually measured in the field.
 

group

A collection of ArcWeb Services users who share the same activation code. Group members can transfer credits and share data.
 

group administrator

The person who sets permissions for the members of an ArcWeb Services group and who is usually the chief contact for the organization.
 

group layer

A group of several layers that appear and act as a single layer. Group layers make it easier to organize a map, assign advanced drawing order options, and share layers for use in other maps.
 

GRS80

Acronym for Geodetic Reference System of 1980. The standard measurements of the earth's shape and size adopted by the International Union of Geodesy and Geophysics in 1979.
 

GSDI

Acronym for global spatial data infrastructure. A global framework of technologies, policies, standards, and human resources necessary to acquire, process, store, distribute, and improve the use of geospatial data across multiple countries and organizations.
 

gsrvr

A process that connects to a relational database management system (RDBMS), using the RDBMS server libraries, and becomes the dedicated link for a GIS client to the database. A gsrvr process is only used in three-tiered geodatabase connections. The GIS client sends instructional commands to the gsrvr process on how to build appropriate SQL statements to perform the requested spatial action (pan, zoom, and so on).
 

GUI

Acronym for graphical user interface. A software display of program options that allows a user to choose commands by pointing to icons, dialog boxes, and lists of menu items on the screen, typically using a mouse. This contrasts with a command line interface in which control is accomplished via the exchange of strings of text.
 

GUID

Acronym for globally unique identifier. A string used to uniquely identify an interface, class, type library, component category, or record.

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H

hachure

A short line on a map that indicates the direction and steepness of a slope. Hachures that represent steep slopes are short and close together; hachures that represent gentle slopes are longer, lighter, and farther apart. Contours, shading, and hypsometric tints have largely replaced hachuring on modern maps.
 

hachured contour

On a topographic map, concentric contour lines drawn with hachures to indicate a closed depression or basin. Concentric contour lines drawn without hachure marks indicate a hill.
 

halftone image

A continuous tone image photographed through a fine screen that converts it into uniformly spaced dots of varying size while maintaining the gradations of highlight and shadow. The size of the dots varies in proportion to the intensity of the light passing through them.
 

Hamiltonian circuit

A path through a network that visits each junction in the network only once and then returns to its point of origin. Hamiltonian circuits are named after the Irish mathematician, physicist, and astronomer William Rowan Hamilton.
 

Hamiltonian path

A path through a network that visits each junction in the network only once without returning to its point of origin. Hamiltonian paths are named after the Irish mathematician, physicist, and astronomer William Rowan Hamilton.
 

hardware key

A small hardware device that provides the unique number used in the generation of a license file. The key is plugged into either the parallel or USB port on the License Manager Server. UNIX users of ArcGIS software do not need a hardware key. Hardware keys are also called dongles.
 

HARN

Acronym for High Accuracy Reference Network. A regional or statewide resurvey and readjustment of NAD 1983 control points using GPS techniques. The resurvey date is often included as part of the datum name: NAD 1983 (1991) or NAD91.
 

hatch class

In linear referencing, a group or category of hatch definitions.
 

hatch definition

In linear referencing, a specification for where hatch marks are drawn on a line feature. Each hatch definition has its own set of properties that include the multiple of the hatch interval at which the hatches in the hatch definition will be placed, the line or marker symbol of the hatches, and whether the hatches will be labeled. The use of multiple hatch definitions allows for the design of complex hatching schemes.
 

hatch style

In linear referencing, an organized collection of symbols and settings for the hatch definitions that make up a hatch class. Hatch styles are stored in a style file (.style) and created by the user to maintain standards for displaying hatches on multiple maps with multiple data sources.
 

hatches

In linear referencing, a series of vertical line or marker symbols displayed on top of features at an interval specified in route measure units.
 

hatching

In linear referencing, a type of labeling that posts and labels hatches or symbols at a regular interval along measured line features.
 

HDOP

Acronym for horizontal dilution of precision. A measure of the geometric quality of a GPS satellite configuration in the sky. HDOP is a factor in determining the relative accuracy of a horizontal position. The smaller the DOP number, the better the geometry.
 

heading

The direction of a moving object, expressed as an angle from a known direction, usually north.
 

heads-up digitizing

Manual digitization by tracing a mouse over features displayed on a computer monitor, used as a method of vectorizing raster data.
 

heap

In computer programming, a variation on the binary tree data structure in which each node's value is greater than the value of its leaf nodes. Sorting data in a heap allows an element to be located more quickly than it could be found in an ordinary list.
 

hectare

A metric areal unit of measure equal to 10,000 square meters. One hectare is equal to 100 ares or 2.47 acres.
 

height

The vertical distance between two points, or above a specified datum.
 

Helmert transformation

A geometric transformation that scales, rotates, or translates images or coordinates between any two Euclidean spaces. It is commonly used in GIS to transform maps between coordinate systems. In a Helmert transformation, parallel lines remain parallel. The midpoint of a line segment remains a midpoint, and all points on a straight line remain on a straight line. The Helmert transformation is named for the German mathematician and geodesist Friedrich Robert Helmert (1843-1917).
 

Help Node

In ArcGIS 8.3 and previous versions, a branch in the ArcToolbox tree providing overview help for ArcToolbox toolsets.
 

hemisphere

Half of a celestial body, such as the earth.
 

heuristic

In computer science, an algorithm that incorporates a shortcut or simplification for solving a programming problem, such as searching. While a heuristic may run faster than a more rigorous algorithm, there is no guarantee that it will find the best solution.
 

hexadecimal

A number system using base 16 notation, usually comprised of the digits 0–9 and the letters A–F or a–f.
 

hierarchical database

A database that stores related information in a tree-like structure, where records can be traced to parent records, which in turn can be traced to a root record.
 

hierarchy

A type of network attribute for a network element in a network dataset. Hierarchy can be used during network analysis to assign priority to a network element. For example, in a transportation network dataset, a "road class" hierarchy can be assigned to edges to favor major roads instead of local streets.
 

High Accuracy Reference Network

A regional or statewide resurvey and readjustment of NAD 1983 control points using GPS techniques. The resurvey date is often included as part of the datum name: NAD 1983 (1991) or NAD91.
 

High Precision Geodetic Network

A regional or statewide resurvey and readjustment of NAD 1983 control points using GPS techniques. The resurvey date is often included as part of the datum name: NAD 1983 (1991) or NAD91.
 

high-level language

A programming language that uses keywords and statements that are similar to expressions in human language or mathematics and is, therefore, easier for people to comprehend and use. A high-level language is named for the high level of abstraction it affords developers over low-level processor functions such as memory access and register storage, meaning such operations do not demand the developer's attention.
 

high-pass filter

In digital image processing, a spatial filter that blocks low-frequency (long-wave) radiation, resulting in a sharpened image.
 

hillshading

Shadows drawn on a map to simulate the effect of the sun's rays over the varied terrain of the land.
 

histogram

A graph showing the distribution of values in a set of data. Individual values are displayed along a horizontal axis, and the frequency of their occurrence is displayed along a vertical axis.
 

histogram equalization

The redistribution of pixel values in an image so that each range contains approximately the same number of pixels. A histogram showing this distribution of values would be nearly flat.
 

historic parcel

In Survey Analyst - Cadastral Editor, a parcel that has been replaced with a new parcel by subdivision, merge, or other means due to a change in the survey record.
 

historical marker

In ArcMap, a user-created reference to a time and date stamp. Historical markers can be used to easily connect to a historical version for a specific date and time.
 

historical version

In ArcMap, a version that a user connects to by using a historical marker or indicating a particular date and time. Once connected, the version provides a read-only view of the geodatabase for the chosen time.
 

history model

A model created, dated, and saved when the application is closed to document the tools and parameter values used for each session. The history model is contained within the history toolbox and can be viewed when the application is reopened.
 

HKCR

HKEY_CLASSES_ROOT registry hive. A Windows registry root key that points to the HKEY_LOCAL_MACHINE\Software\Classes registry key. It displays essential information about OLE and association mappings to support drag-and-drop operations, Windows shortcuts, and core aspects of the Windows user interface.
 

hole

A small gap in a raster line feature, usually considered to be an error caused by the poor quality of a source document or by the scanning process.
 

honor

In network datasets, a type of junction connectivity policy in which junctions connect to other junctions based on the edge connectivity policy set by the user; junctions "honor" the existing edge connectivity policy.
 

horizon

The apparent or visible junction of land and sky.
 

horizon circle

The circle containing all points equidistant from the center of an azimuthal projection.
 

horizontal angle

The angle formed by the intersection of two lines in a horizontal plane.
 

horizontal control

A network of known horizontal geographic positions, referenced to geographic parallels and meridians or to other lines of orientation such as plane coordinate axes.
 

horizontal control datum

A geodetic datum for any extensive measurement system of positions, usually expressed as latitude-longitude coordinates, on the earth's surface. A horizontal geodetic datum may be local or geocentric. If it is local, it specifies the shape and size of an ellipsoid representing the earth, the location of an origin point on the ellipsoid surface, and the orientation of x- and y-axes relative to the ellipsoid. If it is geocentric, it specifies the shape and size of an ellipsoid, the location of an origin point at the intersection of x-,y-, and z-axes at the center of the ellipsoid, and the orientation of the x-,y-, and z-axes relative to the ellipsoid. Examples of local horizontal geodetic datums include the North American Datum of 1927, the European Datum of 1950, and the Indian datum of 1960; examples of geocentric horizontal geodetic datums include the North American Datum of 1983 and the World Geodetic System of 1984.
 

horizontal datum

A geodetic datum for any extensive measurement system of positions, usually expressed as latitude-longitude coordinates, on the earth's surface. A horizontal geodetic datum may be local or geocentric. If it is local, it specifies the shape and size of an ellipsoid representing the earth, the location of an origin point on the ellipsoid surface, and the orientation of x- and y-axes relative to the ellipsoid. If it is geocentric, it specifies the shape and size of an ellipsoid, the location of an origin point at the intersection of x-,y-, and z-axes at the center of the ellipsoid, and the orientation of the x-,y-, and z-axes relative to the ellipsoid. Examples of local horizontal geodetic datums include the North American Datum of 1927, the European Datum of 1950, and the Indian datum of 1960; examples of geocentric horizontal geodetic datums include the North American Datum of 1983 and the World Geodetic System of 1984.
 

horizontal dilution of precision

A measure of the geometric quality of a GPS satellite configuration in the sky. HDOP is a factor in determining the relative accuracy of a horizontal position. The smaller the DOP number, the better the geometry.
 

horizontal geodetic datum

A geodetic datum for any extensive measurement system of positions, usually expressed as latitude-longitude coordinates, on the earth's surface. A horizontal geodetic datum may be local or geocentric. If it is local, it specifies the shape and size of an ellipsoid representing the earth, the location of an origin point on the ellipsoid surface, and the orientation of x- and y-axes relative to the ellipsoid. If it is geocentric, it specifies the shape and size of an ellipsoid, the location of an origin point at the intersection of x-,y-, and z-axes at the center of the ellipsoid, and the orientation of the x-,y-, and z-axes relative to the ellipsoid. Examples of local horizontal geodetic datums include the North American Datum of 1927, the European Datum of 1950, and the Indian datum of 1960; examples of geocentric horizontal geodetic datums include the North American Datum of 1983 and the World Geodetic System of 1984.
 

host

In a computer network, the computer that contains data being accessed by other computers.
 

hot link

In ArcView 3.x, a tool for associating external files with a feature in a view. When a user clicks a feature in the view with the Hot Link tool, an image, text file, or ArcView document or project displays on screen.
 

HPGN

Acronym for High Accuracy Reference Network. A regional or statewide resurvey and readjustment of NAD 1983 control points using GPS techniques. The resurvey date is often included as part of the datum name: NAD 1983 (1991) or NAD91.
 

HRESULT

A 32-bit integer returned from any member of a COM interface indicating success or failure, often written in hexadecimal notation. An HRESULT can also give information about the error that occurred when calling a member of a COM interface. Visual Basic translates HRESULTS into errors; Visual C++ developers work directly with HRESULT values.
 

HTML

Acronym for Hypertext Markup Language. A markup language used to create Web pages for publication on the Internet. HTML is a system of tags that define the function of text, graphics, sound, and video within a document, and is now an Internet standard maintained by the World Wide Web Consortium.
 

HTML document

A computer file formatted with HTML tags so that it may be viewed in a Web browser and published on the World Wide Web. An HTML document may incorporate text, images, sound, video, and other media components. Characteristically, it also has embedded references, called hypertext links, to other HTML documents. These links enable a person viewing a document in a Web browser to open other documents—which may be stored on other computers anywhere in the world—by clicking on the link using a mouse.
 

HTML viewer

An ArcIMS viewer that uses a single ArcMap image or standard image service. The HTML viewer does not require a Java plug-in.
 

HTTP

Acronym for Hypertext Transfer Protocol. The protocol maintained by the World Wide Web Consortium for communicating between servers and clients to exchange HTML documents across the Internet.
 

HTTPS

Acronym for Hypertext Transfer Protocol (Secure). A variant of HTTP enhanced by a security mechanism. It allows transactions such as e-commerce and data sharing to take place on the World Wide Web in a protected way.
 

hub

A central node in a network for routing goods to their destinations.
 

hue

The dominant wavelength of a color, by which it can be distinguished as red, green, yellow, blue, and so forth.
 

human geography

The field of geography concerning a range of social, cultural, and political aspects of human life as related to their distribution through physical space.
 

hydrographic datum

A plane of reference for depths, depth contours, and elevations of foreshore and offshore features.
 

hydrographic survey

A survey of a water body, particularly of its currents, depth, submarine relief, and adjacent land.
 

hydrography

The measurement and description of water features and their related land areas for the purposes of safe marine navigation.
 

hydrologic cycle

The circulation of water from the earth through the atmosphere and back again. Its major stages are evaporation, condensation, precipitation, run-off, transpiration, infiltration, and percolation.
 

hydrology

The study of water, its behavior, and its movements across and below the surface of the earth, and through the atmosphere.
 

hyperlink

A reference (link) from one point in an electronic document to another document or another location in the same document (the target). Activating the link, usually by clicking it with the mouse, causes the browser to display the target of the link.
 

Hypertext Markup Language

A markup language used to create Web pages for publication on the Internet. HTML is a system of tags that define the function of text, graphics, sound, and video within a document, and is now an Internet standard maintained by the World Wide Web Consortium.
 

Hypertext Transfer Protocol

The protocol maintained by the World Wide Web Consortium for communicating between servers and clients to exchange HTML documents across the Internet.
 

hypsography

The study and representation of elevation and the earth's topography.
 

hypsometric curve

A curve showing the relationship of area to elevation for specified terrain. A hypsometric curve is plotted on a graph on which the x-axis represents surface area and the y-axis represents elevation above or below a datum (normally sea level). The curve shows how much area lies above and below marked elevation intervals.
 

hypsometric map

A map showing relief, whether by contours, hachures, shading, or tinting.
 

hypsometric tinting

Relief or depth depicted by a gradation of colors, usually between contour lines. Each color represents a different range of elevation.
 

hypsometry

The science that determines the spatial distribution of elevations above an established datum, usually sea level.

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I

ICAO

Acronym for International Civil Aviation Organization. A member organization that represents the worldwide body of nations for standardizing flight rules, regulations, and requirements.
 

icon

In MOLE, the innermost graphic component of a graphic. Icons represent the Function ID position of a Symbol ID code.
 

ID

A unique character string or numeric value associated with a particular object.
 

IDE

Acronym for integrated development environment. A software development tool for creating applications, such as desktop and Web applications. IDEs blend user interface design and layout tools with coding and debugging tools.
 

identifier

A unique character string or numeric value associated with a particular object.
 

identify

In ArcGIS, a tool that, when applied to a feature (by clicking it), opens a window showing that feature's attributes.
 

identity

In geoprocessing, a topological overlay that computes the geometric intersection of two datasets. The output dataset preserves all the features of the first dataset plus those portions of the second (polygon) dataset that overlap the first. For example, a road passing through two counties would be split into two arc features, each with the attributes of the road and the county it passes through.
 

identity link

An anchor that prevents the movement of features during rubber sheeting.
 

IDispatch

A generic COM interface that has methods allowing clients to ask which members are supported. Classes that implement IDispatch can be used for late binding and DispID binding, which is a form of early binding.
 

IDL

Acronym for Interface Definition Language. A language used to define COM interfaces. The Microsoft implementation of IDL may also be referred to as MIDL or Microsoft IDL.
 

IDW

An interpolation technique that estimates cell values in a raster from a set of sample points that have been weighted so that the farther a sampled point is from the cell being evaluated, the less weight it has in the calculation of the cell's value.
 

IFSAR

Acronym for interferometric synthetic aperture radar. A dual-antenna radar sensor mounted on an airborne or space-borne platform that collects a remotely sensed radar image, called an interferogram. There is a measured energy shift between the signals received by each antenna, and this interference can be colorized to measure elevation or changes in the topography on the earth's surface.
 

IID

Acronym for interface identifier. A string that provides the unique name of an interface. An IID is a type of globally unique identifier (GUID).
 

illumination

The light incident on a surface or object, either natural or artificial, as determined by the surface's slope and aspect and by the sun's azimuth and altitude.
 

image

A representation or description of a scene, typically produced by an optical or electronic device, such as a camera or a scanning radiometer. Common examples include remotely sensed data (for example, satellite data), scanned data, and photographs.
 

image catalog

A collection of raster datasets defined in a table of any format, in which the records define the individual raster datasets that are included in the catalog. Raster catalogs can be used to display adjacent or overlapping raster datasets without having to mosaic them together into one large file. In ArcView 3.x, raster catalogs were called image catalogs.
 

image coordinate

An x,y coordinate pair specifying the location of a pixel, or cell, in terms of its row and column position. The x-coordinate gives the column number (commonly starting from 0 at the left edge of the data), and the y-coordinate gives the row number (commonly starting from 0 at the top of the data).
 

image data

Data produced by scanning a surface with an optical or electronic device. Common examples include scanned documents, remotely sensed data (for example, satellite images), and aerial photographs. An image is stored as a raster dataset of binary or integer values that represent the intensity of reflected light, heat, or other range of values on the electromagnetic spectrum.
 

image division

A digital image processing technique for increasing the contrast between features in an image by dividing the pixel values in the image by the values of corresponding pixels in a second image. Image division is normally used to identify concentrations of vegetation.
 

image scale

The ratio between a distance in an image and the actual distance on the ground, calculated as focal length divided by the flying height above mean ground elevation. Image scale can vary in a single image from point to point due to surface relief and the tilt of the camera lens.
 

image server

A public ArcIMS virtual server for image services.
 

image service

In ArcIMS, a service that uses the spatial server image rendering capabilities. When a request is received, a map is generated on the server, and the response is sent back as a JPG, PNG, or GIF image. A new map image is generated each time a client requests new information.
 

image service definition

In ArcGIS Image Server, a workspace created using the Image Service Definition Editor toolbar that defines the key properties of a service, including name and default spatial reference system. The image service definition workspace has a .ISDef extension.
 

image service reference file

In ArcGIS Image Server, a file that stores properties for reestablishing a connection to a service and setting up user-defined image service properties. Image service reference files have a .ISRef extension.
 

image space

The x,y coordinate space defined by the number of columns and rows in a raster dataset. The origin of image space is commonly the center of the top left pixel of the data and is labeled (0,0). The x-axis corresponds to the number of columns in the raster, and the y-axis to the number of rows. For raster data to be used in GIS software, image space must be transformed to a real-world coordinate system through georeferencing.
 

imager

Any satellite or aerial instrument that measures and maps the earth and its atmosphere.
 

impedance

A measure of the amount of resistance, or cost, required to traverse a path in a network, or to move from one element in the network to another. Resistance may be a measure of travel distance, time, speed of travel multiplied by distance, and so on. Higher impedance values indicate more resistance to movement, and a value of zero indicates no resistance. An optimum path in a network is the path of lowest impedance, also called the least-cost path.
 

impedance model

In ArcInfo, a routing model that determines the best route by finding the path of least resistance.
 

impersonation

A process by which a Web application assumes the identity of a particular user and thus gains all the privileges to which that user is entitled.
 

implement

In programming an interface, to provide code for each of the methods of an interface (the interface is defined separately).
 

import

To bring data from one computer system or application into another. Importing often involves some form of data conversion.
 

inbound interface

An interface implemented by a class, on which a client can call members.
 

incident

In ArcGIS Network Analyst, a network location used in closest facility analysis. Car accidents, crime scenes, and fires are examples of incidents.
 

incident energy

Electromagnetic radiation that strikes a surface.
 

INCITS

Acronym for International Committee for Information Technology Standards. An ANSI-accredited forum that creates and maintains information and communications technology standards through the participation and consensus of its industry members.
 

independent variable

One or a set of variables used to model or predict the dependent variable. For example, a prediction of annual purchases for a proposed store (the dependent variable) might include independent variables representing the number of potential customers, distance to competition, store visibility, and local spending patterns. In the regression equation, independent variables appear on the right side of the equal sign and are often referred to as explanatory variable.
 

indeterminate flow direction

In networks, a flow direction that is unknown or undiscoverable. Indeterminate flow direction occurs when flow direction cannot be determined from the connectivity of the network, the locations of sources and sinks, and the enabled or disabled states of features.
 

index

A data structure, usually an array, used to speed the search for records in a database or for spatial features in geographic datasets. In general, unique identifiers stored in a key field point to records or files holding more detailed information.
 

index contour line

On a topographic map, a contour line that is thicker than the rest and usually labeled with the elevation that it represents. Depending on the contour interval, every fourth or fifth contour line may be an index contour.
 

index map

A schematic map used as a reference for a collection of map sheets, outlining the total area covered along with the coverage extent of, and usually a name or reference for, each map sheet.
 

industry

An organization with specific GIS needs. Examples of industries include government, transportation, health care, homeland security, and public safety.
 

INFO database

A tabular database management system used by ArcInfo Workstation software to store and manipulate attributes of a GIS dataset in ArcInfo Workstation format. INFO databases are stored inside a workspace folder with subdirectories containing files that represent the geometry and topology that make up a coverage.
 

information space

A geometric representation of relationships between elements in a data domain, in which relative position indicates the degree of similarity between elements. Information spaces are often based on geographic metaphors and are used to provide more intuitive views of a complex, multidimensional data domain.
 

Informix

A commercial relational database management system (RDBMS) supported by ArcSDE.
 

infrared scanner

A device that detects infrared radiation and converts it into an electrical signal that can be recorded on film or magnetic tape.
 

infrastructure

The system of human-made physical structures, such as roads, bridges, canals, cables, wires, communications towers, hospitals, pipes, reservoirs, and sewers, that provide communication, transportation, public services, utilities, or all of the above to a populace.
 

inheritance

In object-oriented programming, the acquisition of methods and properties by child classes or interfaces from their previously existing parent classes or interfaces. Inheritance is one of the defining characteristics of an object-oriented system.
 

in-process

Within the process space of a client application, a class contained in a DLL is in-process, as objects are loaded into the process space of the client EXE. A component contained in a separate EXE is out-of-process.
 

input data

Data that is entered into a computer, device, program, or process.
 

input event record

In geocoding, a piece of information such as a customer address and location of an incident. Input event record types vary by application. They include customer addresses, location of the event or incident, location of equipment and facilities, and the monument offset.
 

input feature

In geoprocessing, data put into the system for processing, usually specified by a path in a dialog box, script, or at the command line.
 

input table

In geoprocessing, tabular data put into the system for processing, usually specified by a path in a dialog box, script, or at the command line.
 

inset map

A small map set within a larger map. An inset map might show a detailed part of the map at a larger scale, or the extent of the existing map drawn at a smaller scale within the context of a larger area.
 

instance

In object-oriented programming, a single object created based on the template or definition of the class to which it belongs.
 

instantiation

In programming, the process of creating a single object based on the template or definition of the class to which it belongs.
 

instrument setup field

In the Survey Analyst for field measurements Survey Explorer, a field that allows the user to select the instrument setup or enter the name of a new instrument setup.
 

integer data

Data that represents phenomena with distinct boundaries. Property lines and streets are examples of discrete data.
 

integrated development environment

A software development tool for creating applications, such as desktop and Web applications. IDEs blend user interface design and layout tools with coding and debugging tools.
 

integrated feature dataset

In geodatabases, a feature dataset that stores topologically associated feature classes. The topological editing tools in ArcMap can be used to maintain the topological associations of features in an integrated feature dataset. Network feature classes do not participate in the topological associations within an integrated feature dataset.
 

integration

A high degree of interconnection between two or more programs or datasets, in which they share a common schema, ontology, semantic approach, or method that allows information to be passed between them without being fully processed.
 

intensity

In the IHS (intensity, hue, saturation) color model, the relative brightness of a color.
 

interactive vectorization

A manual process for converting raster data into vector features that involves tracing raster cells.
 

interchange format

A file format that allows the easy exchange of data between different software programs.
 

Interface Definition Language

A language used to define COM interfaces. The Microsoft implementation of IDL may also be referred to as MIDL or Microsoft IDL.
 

interferogram

A radar image that records interference patterns captured by two antennae a short distance apart.
 

interior feature weight

One of two weights that allow control of how labels are placed relative to polygon features in ArcMap. Higher feature weights prevent labels from being placed over features. A high interior weight prevent labels from occupying the interior of polygon features.
 

intermediate data

Any data in a process that did not exist before the process existed and that will not be maintained after the process executes.
 

international date line

An imaginary line, generally following the meridian of longitude lying 180 degrees east and west of the Greenwich meridian, where the date changes. The time zone east of the international date line is twelve hours ahead of Greenwich mean time; the time zone west of the international date line is twelve hours behind Greenwich mean time. A traveler going west across the date line adds a day; a traveler going east across it subtracts a day.
 

international meridian

The meridian adopted by international agreement in 1884 as the prime meridian, the 0-degree meridian from which all other longitudes are calculated. The Greenwich prime meridian runs through the Royal Observatory in Greenwich, England.
 

International Organization for Standardization

A federation of national standards institutes from 145 countries that works with international organizations, governments, industries, businesses, and consumer representatives to define and maintain criteria for international standards.
 

internationalization

The process of creating software that can be adapted to the requirements of different languages and cultures without substantive changes to the source code.
 

Internet

The global network of computers that communicate through common protocols, such as TCP/IP.
 

interoperability

The capability of components or systems to exchange data with other components or systems, or to perform in multiple environments. In GIS, interoperability is required for a GIS user using software from one vendor to study data compiled with GIS software from a different provider.
 

interpolation

The estimation of surface values at unsampled points based on known surface values of surrounding points. Interpolation can be used to estimate elevation, rainfall, temperature, chemical dispersion, or other spatially-based phenomena. Interpolation is commonly a raster operation, but it can also be done in a vector environment using a TIN surface model. There are several well-known interpolation techniques, including spline and kriging.
 

interrupted projection

A world projection that reduces distortion by dividing the projected area into gores, each with its own central meridian.
 

intersect

A geometric integration of spatial datasets that preserves features or portions of features that fall within areas common to all input datasets.
 

intersection

The point where two lines cross. In geocoding, most often a street crossing.
 

intersection connector

A character used in address data to indicate that an address is located at an intersection. For example, in the address "S. Huntington Dr. & E. Clark Blvd." the ampersand (&) character is the intersection connector. The intersection connector delimits the address into two parts and assigns intersection searches to the address.
 

intranet

A computer network, often using the same software and serving the same functions as those found on the Internet, that is restricted to users within an organization.
 

intrinsic stationarity

In spatial statistics, the assumption that a set of data comes from a random process with a constant mean and a semivariogram that depends only on the distance and direction separating any two locations.
 

inverse distance

One divided by distance, often raised to some power (1/D or 1/D2, for example), where D is a distance value. By inverting the distance among spatial features, and using that inverted value as a weight, near things have a larger weight or influence than things that are farther away.
 

inverse distance weighted interpolation

An interpolation technique that estimates cell values in a raster from a set of sample points that have been weighted so that the farther a sampled point is from the cell being evaluated, the less weight it has in the calculation of the cell's value.
 

IP address

Acronym for Internet protocol address. A unique number, such as 10.48.6.8, that identifies each computer on the Internet. IP addresses are similar to phone numbers, and allow data to travel between one computer and another via the Internet.
 

irregular triangular mesh

A vector data structure that partitions geographic space into contiguous, nonoverlapping triangles. The vertices of each triangle are sample data points with x-, y-, and z-values. These sample points are connected by lines to form Delaunay triangles. TINs are used to store and display surface models.
 

irregular triangular surface model

A vector data structure that partitions geographic space into contiguous, nonoverlapping triangles. The vertices of each triangle are sample data points with x-, y-, and z-values. These sample points are connected by lines to form Delaunay triangles. TINs are used to store and display surface models.
 

isanomal

A line on a map connecting points of equal difference from a normal value, usually a meteorological value such as average temperature.
 

isarithm

An isoline drawn according to values that can occur at points; an isometric line.
 

ISO

Abbreviation for International Organization for Standardization. A federation of national standards institutes from 145 countries that works with international organizations, governments, industries, businesses, and consumer representatives to define and maintain criteria for international standards.
 

isobar

A line on a weather map connecting places of equal barometric pressure.
 

isochrone

A line on a map connecting points of equal elapsed time; especially, travel time to or from a given location.
 

isohyet

A line on a map connecting points of equal rainfall.
 

isolation level

A setting in a database management system (DBMS) that defines how much an application process is isolated from other concurrently executing processes in a DBMS. It specifies the degree to which the rows read and updated by the application are available to other concurrently executing processes. It also specifies the degree to which updates from other concurrently executing application processes are available to the application.
 

isoline

A line connecting points of equal value on a map. Isolines fall into two classes: those in which the values actually exist at points, such as temperature or elevation values, and those in which the values are ratios that exist over areas, such as population per square kilometer or crop yield per acre. The first type of isoline is specifically called an isometric line or isarithm; the second type is called an isopleth.
 

isometric line

An isoline drawn according to known values, either sampled or derived, that can occur at points. Examples of sampled quantities that can occur at points are elevation above sea level, an actual temperature, or an actual depth of precipitation. Examples of derived values that can occur at points are the average of temperature over time for one point or the ratio of smoggy days to clear days for one point.
 

isopleth

An isoline drawn according to known values that can only be recorded for areas, not points. Examples include population per square mile or the ratio of residential land to total land for an area.
 

isotherm

A line on a map connecting points of equal temperature.
 

isotropic

Having uniform spatial distribution of movement or properties, usually across a surface.
 

isotropy

A property of a natural process or data where spatial dependence (autocorrelation) changes only with the distance between two locations—direction is unimportant.
 

item

An element in the Catalog tree. Items include data sources, such as shapefiles and geodatabases, and nonspatial elements, such as folders.
 

iterative procedure

A repetitive or recurring procedure.
 

IUnknown

All COM interfaces inherit from the IUnknown interface. The default implementation of IUnknown controls object lifetime and provides runtime type support.

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J

J2ME

The Java platform edition developed by Sun Microsystems for small, stand-alone, or connectable devices. Java ME enables development, deployment, and management of applications that can scale from mobile devices to desktop computers. In 2007, Sun replaced J2ME with Java ME. 
 

jaggies

The jagged appearance of curves and diagonal lines in a raster image. Aliasing becomes more apparent as the size of the raster pixels is increased or the resolution of the image is decreased. 
 

Java

An object-oriented cross-platform programming language developed by Sun Microsystems. 
 

Java 2 Platform, Micro Edition

The Java platform edition developed by Sun Microsystems for small, stand-alone, or connectable devices. Java ME enables development, deployment, and management of applications that can scale from mobile devices to desktop computers. In 2007, Sun replaced J2ME with Java ME. 
 

Java Connector

An ArcIMS Application Server Connector. It can be used with Java Server Pages (JSP) or as part of a Java applet or application. 
 

Java ME

The Java platform edition developed by Sun Microsystems for small, stand-alone, or connectable devices. Java ME enables development, deployment, and management of applications that can scale from mobile devices to desktop computers. In 2007, Sun replaced J2ME with Java ME. 
 

Java ME Wireless Toolkit

A toolkit for building applications that run on devices compliant with the Java specification for wireless devices. 
 

Java viewer

An ArcIMS viewer that uses a Java 2 applet. The Java viewer can be used with feature or image services. It allows client-side drawing and editing and requires a Java plug-in. 
 

JavaScript

A scripting language that runs within a Web browser and interacts with HTML code to enable Web developers to add functionality to their Web sites. 
 

JavaServer Faces

A framework for building user interfaces for Java Web applications. 
 

JavaServer Pages

A Java technology that enables rapid development of platform-independent, Web-based applications. JSP separates the user interface from content generation, enabling designers to change the overall page layout without altering the underlying dynamic content. 
 

JavaServer Pages Standard Tag Library

A Java technology that encapsulates core functionality common to many Web-based applications as simple tags. JSTL includes tags for structural tasks such as iteration and conditionals, manipulation of XML documents, internationalization and locale-sensitive formatting, and SQL. 
 

JDK

Acronym for Java Development Kit. A set of Java development tools from Sun Microsystems that provide basic tools needed for writing, testing, and debugging Java applications and applets. 
 

Jenks' optimization

A method of statistical data classification that partitions data into classes using an algorithm that calculates groupings of data values based on the data distribution. Jenks' optimization seeks to reduce variance within groups and maximize variance between groups. 
 

job

A task scheduled on a computer for immediate or future processing. A job can involve a single task or a batch mode operation. 
 

job book

In Survey Analyst - Cadastral Editor, a tool that facilitates the viewing and management of cadastral fabric jobs. 
 

Job Tracking for ArcGIS

ESRI software used to track and manage database production workflow. It provides the ability to define tasks, set up production environments, manage geodatabase versioning and track database changes at the feature level. JTX also provides tools for allocating resources and tracking the status and progress of jobs. 
 

JOG

Acronym for joint operations graphic. A 1:250,000-scale topographic map used by militaries worldwide. Joint operations graphics use a common base graphic to facilitate operations involving air, ground, and naval forces. 
 

joined parcel

In Survey Analyst - Cadastral Editor, a parcel that is connected to the cadastral fabric, and shares common points with neighboring parcels. 
 

joining

Appending the fields of one table to those of another through an attribute or field common to both tables. A join is usually used to attach more attributes to the attribute table of a geographic layer. 
 

joint operations graphic

A 1:250,000-scale topographic map used by militaries worldwide. Joint operations graphics use a common base graphic to facilitate operations involving air, ground, and naval forces. 
 

JPEG

Acronym for Joint Photographic Experts Group. A lossy image compression format commonly used on the Internet. JPEG is well-suited for photographs or images that have graduated colors. 
 

JSF

A framework for building user interfaces for Java Web applications. 
 

JSON

Acronym for JavaScript Object Notation. A lightweight, human-readable data interchange format. An alternative to XML, JSON is language independent but relies on common programming language structures such as objects and arrays. 
 

JSP

Acronym for JavaServer Pages. A Java technology that enables rapid development of platform-independent, Web-based applications. JSP separates the user interface from content generation, enabling designers to change the overall page layout without altering the underlying dynamic content. 
 

JSTL

A Java technology that encapsulates core functionality common to many Web-based applications as simple tags. JSTL includes tags for structural tasks such as iteration and conditionals, manipulation of XML documents, internationalization and locale-sensitive formatting, and SQL. 
 

JTX

Acronym for Job Tracking for ArcGIS. ESRI software used to track and manage database production workflow. It provides the ability to define tasks, set up production environments, manage geodatabase versioning and track database changes at the feature level. JTX also provides tools for allocating resources and tracking the status and progress of jobs. 
 

junction

For network data models in a geodatabase, a point at which two or more edges meet.
 

junction connectivity policy

In network datasets, a connectivity policy that defines how a junction may connect to an edge. There are two junction connectivity policies: honor and override. 
 

junction element

For network data models in a geodatabase, a point at which two or more edges meet. 

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K

kernel

On a raster, an analysis boundary or processing window within which cell values affect calculations and outside which they do not. Filters are used mainly in cell-based analysis where the value of a center cell is changed to the mean, the sum, or some other function of all cell values inside the filter. A filter moves systematically across a raster until each cell has been processed. Filters can be of various shapes and sizes, but are most commonly three-cell by three-cell squares. 
 

key

An attribute or set of attributes in a database that uniquely identifies each record. 
 

key attribute

An attribute or set of attributes in a database that uniquely identifies each record. A primary key allows no duplicate values and cannot be null. 
 

keyboard shortcut

A keystroke combination that executes a command that might otherwise require the use of a mouse. For example, Ctrl+C is a well-known keyboard shortcut for copying a selection in Windows. 
 

keycode

A unique number in the feature line of a license or authorization file that controls access to software. Keycodes are based on a unique identifier. In ArcEditor Concurrent Use on Windows, for example, the hardware key number provides this unique identifier. The License Manager compares the keycodes in the license file and the unique identifier for a computer to allow access to the software. If the keycode and the unique identifier agree, then software access is granted. 
 

keyframe

In an animation in ArcMap, ArcScene, or ArcGlobe, a snapshot of an object's properties at a certain time. 
 

keyword

A significant word from a document that is used to index or search content. 
 

kinematic positioning

Determining the position of an antenna on a moving object such as a ship or an automobile. 
 

knockout

In offset printing, an area that has been defined to cut through or mask specific layers of colored inks. Knockouts are used to ensure that certain ink colors are not mixed with inks that are laid down after them. 
 

knowledge base

A database of information about a subject, used in expert systems. 
 

known point

A surveyed point that has an established x,y coordinate value. Known points are used in survey operations to extend survey computations into a project area. 
 

Kohonen map

A map that uses a neural network algorithm to classify and illustrate associations in complex datasets, and reveal multidimensional patterns. A similar set of methods produces maps referred to as self-organizing maps (SOMs). Kohonen maps are named for the Finnish engineer Teuvo Kohonen. 
 

kriging

An interpolation technique in which the surrounding measured values are weighted to derive a predicted value for an unmeasured location. Weights are based on the distance between the measured points, the prediction locations, and the overall spatial arrangement among the measured points. Kriging is unique among the interpolation methods in that it provides an easy method for characterizing the variance, or the precision, of predictions. Kriging is based on regionalized variable theory, which assumes that the spatial variation in the data being modeled is homogeneous across the surface. That is, the same pattern of variation can be observed at all locations on the surface. Kriging was named for the South African mining engineer Danie G. Krige (1919-). 

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L

label

In cartography, text placed on or near a map feature that describes or identifies it. 
 

label class

In ArcMap, a category of labels that represents features with the same labeling properties. For example, in a roads layer, label classes could be created to define information and style for each type of road: interstate, state highway, county road, and so on. 
 

label engine

In ArcMap, the software used to place labels. 
 

label expression

A statement that determines the label text. Label expressions typically concatenate or modify the contents of one or more fields, and may add additional text strings to create more informative labels. They can contain Visual Basic script or JScript to add logic, text processing, and formatting for the labels. 
 

Label Fitting Strategy tab

In Maplex for ArcGIS, a tab on the Label Placement dialog box that allows control of the ways the label engine can fit more labels into a limited area. Methods that can increase label placement are stacking labels, reducing the font size of labels in congested areas, or abbreviating labels. 
 

Label Manager

In ArcMap, the tool used to display and set labeling properties for the currently active data frame. The Label Manager is accessible through the Labeling toolbar. 
 

label offset

The distance a label should be from the feature it labels. A label offset and a maximum label offset can be set for point features. Maximum label offsets are expressed as a percentage of the label offset. For line features, a label offset can be set from the line (similar to the label offset for point features) and along the line (which controls the position of the label relative to the ends of the line). Label offsets are not available for all label position options. 
 

label offset constraint

The maximum distance away from a point feature that a label may be placed, beyond the specified offset. 
 

label orientation

The angle or direction of alignment for feature labels. Labels for features are usually placed horizontally, but they may also be oriented to an angle stored as an attribute, an angle defined by the orientation of the feature geometry, or along the graticule of the data frame. 
 

label placement option

A parameter used to define a placement property for a label. Label placement properties include such properties as label offset, label placement zone, label fitting strategy, label prioritiy, label stacking, and label weight. 
 

label placement property

A parameter used to define a placement property for a label. Label placement properties include such properties as label offset, label placement zone, label fitting strategy, label prioritiy, label stacking, and label weight. 
 

label placement zone

One of eight designated areas on a map, radiating from a point, in which labels may be placed. The user can indicate in which of eight zones labels should be placed, relative to the point. These preferences are taken into account when placing point labels using the Best Position placement option. 
 

label point

In a coverage, a feature class used to represent points or identify polygons. When representing points, the x,y location of the point describes the location of the feature. When identifying polygons, the point can be located anywhere within the polygon. 
 

Label Position tab

In Maplex for ArcGIS, a tab on the Label Placement dialog box that allows control of how labels are placed relative to features. The position of a label is determined by such parameters as: the orientation, offset, and position style for a given feature geometry. 
 

label priority

In ArcGIS, a ranking system that determines the order in which labels will be placed on a map. Labels with higher priority will be placed before labels with lower priority. Labels placed last will have a greater chance of being crowded out or placed in an alternate position. 
 

label rule

A parameter used to define a placement property for a label. Label placement properties include such properties as label offset, label placement zone, label fitting strategy, label prioritiy, label stacking, and label weight. 
 

label stacking

The splitting of long labels to place the text on two or more lines. Maplex for ArcGIS allows specification of which characters trigger a split and whether or not they show up in the label. 
 

label weight

An ESRI Standard Label Engine ranking system that indicates whether labels from a given label class may be covered by another label in cases in which label placement conflicts occur. Labels with higher weight are less likely to be overlapped than labels with lower weight. 
 

lag

In the creation of a semivariogram, the sample distance used to group or bin pairs of points. Using an appropriate lag distance can be helpful in revealing scale-dependent spatial correlation. 
 

LAN

Acronym for local area network. Communications hardware and software that connect computers in a small area, such as a room or a building. Computers in a LAN can share data and peripheral devices, such as printers and plotters, but do not necessarily have a link to outside computers. 
 

land cover

The classification of land according to the vegetation or material that covers most of its surface; for example, pine forest, grassland, ice, water, or sand. 
 

land information system

A geographic information system for cadastral and land-use mapping, typically used by local governments. 
 

land use

The classification of land according to what activities take place on it or how humans occupy it; for example, agricultural, industrial, residential, urban, rural, or commercial. 
 

landform

Any natural feature of the land having a characteristic shape, including major forms such as plains and mountains and minor forms such as hills and valleys. 
 

landmark

Any prominent natural or artificial object in a landscape used to determine distance, bearing, or location. 
 

Landsat

Multispectral, earth-orbiting satellites developed by NASA (National Aeronautics and Space Administration) that gather imagery for land-use inventory, geological and mineralogical exploration, crop and forestry assessment, and cartography. 
 

landscape ecology

The study of spatial patterns, processes, and change across biological and cultural structures within areas encompassing multiple ecosystems. 
 

large scale

Generally, a map scale that shows a small area on the ground at a high level of detail. 
 

large-format printer

A printing device capable of producing an image on large paper or other media sized between 36 and 87 inches (91 and 220 centimeters) wide. Modern large format printers typically use inkjet printing technology to print an image on a roll of paper that is automatically cut to the desired length. Large-format printers may also be called plotters or wide-format printers. 
 

LAS

An industry-standard binary file format that maintains information related to lidar data. 
 

late binding

A COM technique that an application uses for determining an object's properties and methods at run time, rather than when the code is compiled. Late binding is generally used by scripting languages. 
 

latitude

The angular distance, usually measured in degrees north or south of the equator. Lines of latitude are also referred to as parallels. 
 

latitude of center

The latitude value that defines the center, and sometimes the origin, of a projection. 
 

latitude of origin

The latitude value that defines the origin of the y-coordinate values for a projection. 
 

latitude-longitude

A reference system used to locate positions on the earth's surface. Distances east–west are measured with lines of longitude (also called meridians), which run north–south and converge at the north and south poles. Distance measurements begin at the prime meridian and are measured positively 180 degrees to the east and negatively 180 degrees to the west. Distances north–south are measured with lines of latitude (also called parallels), which run east–west. Distance measurements begin at the equator and are measured positively 90 degrees to the north and negatively 90 degrees to the south. 
 

lattice

A representation of a surface using an array of regularly spaced sample points (mesh points) that are referenced to a common origin and have a constant sampling distance in the x and y directions. Each mesh point contains the z-value at that location, which is referenced to a common base z-value, such as sea level. Z-values for locations between lattice mesh points can be approximated by interpolation based on neighboring mesh points. 
 

layer

The visual representation of a geographic dataset in any digital map environment. Conceptually, a layer is a slice or stratum of the geographic reality in a particular area, and is more or less equivalent to a legend item on a paper map. On a road map, for example, roads, national parks, political boundaries, and rivers might be considered different layers. 
 

layer file

In ArcGIS, a file with a .lyr extension that stores the path to a source dataset and other layer properties, including symbology. 
 

layout

The arrangement of elements on a map, possibly including a title, legend, north arrow, scale bar, and geographic data. 
 

layout view

In ArcMap and ArcReader, a view that shows the virtual page upon which geographic data and map elements, such as titles, legends, and scale bars, are placed and arranged for printing. 
 

L-band

The group of radio frequencies that carry data from GPS satellites to GPS receivers. 
 

LBS

Information or a physical service delivered to multiple channels, exclusively based on the determined location of a wireless device. Some location-based applications include emergency services, information services, and tracking services. 
 

leader

In MOLE, typically two or more force elements grouped together and placed on a line based on user-specified rules. Leaders are often used to clean up the map display in cases where many symbols overlap, to group related units together, and to define perimeters or areas of interest for formations. 
 

least convex hull

The smallest convex polygon that encloses a group of objects, such as points. In ArcGIS, TIN boundaries are convex hulls by default. 
 

least-cost path

The path between two locations that costs the least to traverse, where cost is a function of time, distance, or some other criteria defined by the user. 
 

least-squares adjustment

A statistical method for providing a best fit for survey point locations and detecting measurement error by minimizing the sum of the squares of measurement residuals. The method allows many measurements to participate simultaneously in a single computation. 
 

least-squares corrections

The final measurement residuals of a least squares adjustment. 
 

left-right topology

The topological data structure in an ArcInfo coverage that stores, for each arc, the identity of the polygons to the left and right of it. Left-right topology supports analysis functions, such as adjacency. 
 

legend

The description of the types of features included in a map, usually displayed in the map layout. Legends often use graphics of symbols or examples of features from the map with a written description of what each symbol or graphic represents. 
 

legend patch shape

The geometric shape of either a line or a polygon that is used to represent a specific kind of feature in a legend and in the ArcMap table of contents. 
 

level of confidence

In a statistical test, the risk, expressed as a percentage, that the null hypothesis will be incorrectly rejected because of sampling error when the null hypothesis is true. For example, a confidence level of 95 percent means that if the same test were performed 100 times on 100 different samples, the null hypothesis would be incorrectly rejected five times. 
 

level of detail

An abstraction of a layer in ArcGlobe portraying the layer at some degree of resolution between simplified and unsimplified. 
 

level of significance

In statistical testing, the probability of an incorrect rejection of the null hypotheses. 
 

leveling

In surveying, the measurement of the heights of objects and points according to a specified elevation, usually mean sea level. 
 

LIBID

Acronym for Library Identifier. A type of GUID consisting of a unique string assigned to a type library. 
 

library

In object-oriented programming, a logical grouping of classes, usually with a header section that lists the classes in the library. 
 

license

The grant to a party of the right to use a software package or component. A license differs from a sale in that the user does not necessarily purchase the software but is granted the legal right to use it. 
 

license file

A file that contains License Manager license data. Each license file contains information such as the SERVER, ESRI_SENTINEL_KEY number (Windows only), Version, the number of seats, and so on. 
 

lidar

Acronym for light detection and ranging. A remote-sensing technique that uses lasers to measure distances to reflective surfaces. 
 

lighting normal

In ArcScene and ArcGlobe, vectors normal to a geometry's surface, stored in that geometry to help define how lighting affects it. 
 

limits

In Survey Analyst for field measurements, restrictions that define an acceptable level of measurement error for each computation. 
 

line

On a map, a shape defined by a connected series of unique x,y coordinate pairs. A line may be straight or curved. 
 

line connection

A procedure that combines groups of individual lines with the same name into a single line for the label engine. This is often necessary because lines such as roads and rivers are usually digitized as many small segments that must be connected together to represent a single real-world feature. 
 

line event

In linear referencing, a description of a portion of a route using a from- and to-measure value. Examples of line events include pavement quality, salmon spawning grounds, bus fares, pipe widths, and traffic volumes. 
 

line feature

A map feature that has length but not area at a given scale, such as a river on a world map or a street on a city map. 
 

line of sight

A line drawn between two points, an origin and a target, that is compared against a surface to show whether the target is visible from the origin and, if it is not visible, where the view is obstructed. 
 

line simplification

A generalization technique in which vertices are selectively removed from a line feature to eliminate detail while preserving the line's basic shape. 
 

line smoothing

The process of adding extra points to lines to reduce the sharpness of angles between line segments, resulting in a smoother appearance. 
 

lineage

A collection of states representing the changes that have occurred over time in a versioned geodatabase. 
 

linear dimension

A measurement of the horizontal or vertical dimension of a feature. Linear dimensions may not represent the true distance between beginning and ending dimension points because they do not take angle into account as aligned dimensions do. 
 

linear feature

A map feature that has length but not area at a given scale, such as a river on a world map or a street on a city map. 
 

linear interpolation

The estimation of an unknown value using the linear distance between known values. 
 

linear referencing

A method for storing geographic data by using a relative position along an already existing line feature; the ability to uniquely identify positions along lines without explicit x,y coordinates. In linear referencing, location is given in terms of a known line feature and a position, or measure, along the feature. Linear referencing is an intuitive way to associate multiple sets of attributes to portions of linear features. 
 

linear unit

The unit of measurement on a plane or a projected coordinate system, often meters or feet. 
 

line-on-line overlay

In linear referencing, the overlay of two line event tables to produce a single line event table. The new event table can be the logical intersection or union of the input tables. 
 

line-on-point overlay

In linear referencing, the overlay of a line event table and a point event table to produce a single point event table. The new event table can be the logical intersection or union of the input tables. 
 

link

In georeferencing, connections added between known points in a dataset being georeferenced and corresponding points in the dataset being used as a reference. 
 

Link command

In Survey Analyst for field measurements, a command that finds nearby survey points for each feature vertex and automatically creates links. The command allows the user to specify the search tolerance for finding the survey points. With the Link command, users may perform batch links; it is useful to use if there are many unlinked features that need to be associated with nearby survey points. 
 

link lines

In Survey Analyst for field measurements, lines displayed on a map after a survey point and a feature vertex are linked. 
 

Link tool

In Survey Analyst for field measurements, a tool that allows the user to make a link between a survey point and a feature vertex by snapping and clicking a feature vertex, then snapping to and clicking the related survey point. With the Link tool, users must make each individual link manually. 
 

LIS

A geographic information system for cadastral and land-use mapping, typically used by local governments. 
 

List page

In Survey Analyst for field measurements, one of two types of pages in the Survey Explorer. The List page lists multiple survey objects. 
 

little endian

A computer hardware architecture in which, within a multibyte numeric representation, the least significant byte has the lowest address and the remaining bytes are encoded in increasing order of significance. 
 

load balance

The act of distributing application, network, and/or server resources to optimize performance. 
 

load distribution

The act of distributing application, network, and/or server resources to optimize performance. 
 

local analysis

The computation of an output raster where the output value at each location is a function of the input value at the same location. 
 

local area network

Communications hardware and software that connect computers in a small area, such as a room or a building. Computers in a LAN can share data and peripheral devices, such as printers and plotters, but do not necessarily have a link to outside computers. 
 

Local check method

In Survey Analyst for field measurements, one of two ways to apply the Coordinate Out of Tolerance command. The Local check method searches for coordinates out of tolerance within each survey project. 
 

local datum

A horizontal geodetic datum that serves as a basis for measurements over a limited area of the earth; that has its origin at a location on the earth's surface; that uses an ellipsoid whose dimensions conform well to its region of use; and that was originally defined for land-based surveys. A local datum in this sense stands in contrast to a geocentric datum. Examples include the North American Datum of 1927 and the Australian Geodetic Datum of 1966. 
 

local functions

The computation of an output raster where the output value at each location is a function of the input value at the same location. 
 

local polynomial interpolation

In ArcGIS Geostatistical Analyst, a deterministic interpolation method. The interpolated surface is not required to conform to the sample data points, and the method does not have standard errors associated with it. 
 

localization

The process of adapting software to the requirements of a different language or culture, including translating user interfaces, documentation, and help systems; customizing features; and accommodating different character sets. 
 

location

An identifier assigned to a region or feature. 
 

Location Aware Services

Services that allow IBM WebSphere Everywhere Access (WEA) application providers to use location-based services from multiple vendors, by providing an application programming interface (API). 
 

location query

A statement or logical expression that selects geographic features based on location or spatial relationship. For example, a spatial query might find which points are contained within a polygon or set of polygons, find features within a specified distance of a feature, or find features that are adjacent to each other. 
 

Location Utility Service

An OpenLS ArcWeb service used to find geographical coordinates of an address and to find an address based on the geographical coordinates (geocoding/reverse geocoding). 
 

location-allocation

The process of finding the best locations for one or more facilities that will service a given set of points and then assigning those points to the facilities, taking into account factors such as the number of facilities available, their cost, and the maximum impedance from a facility to a point. 
 

location-based services

Information or a physical service delivered to multiple channels, exclusively based on the determined location of a wireless device. Some location-based applications include emergency services, information services, and tracking services. 
 

locked parcel

In Survey Analyst - Cadastral Editor, a parcel that has been locked for editing. Locked parcels cannot be edited simultaneously in a multiuser environment. 
 

locomotion

The movements of a person following a route. Locomotion is the physical component of navigation. 
 

log file

A database file that records changes in data, often used as part of a database restoration. 
 

logarithm

The power to which a fixed number (the base) must be raised to equal a given number. The three most frequently used bases for logarithms are base 10, base e, and base 2. 
 

logical expression

A string of numbers, constants, variables, operators, and functions that returns a value of true or false. 
 

logical network

An abstract representation of a network, implemented as a collection of hidden tables. A logical network contains edge, junction, and turn elements, the connectivity between them, and the weights necessary for traversing the network. It does not contain information about the geometry or location of its elements; this information is one of the components of a network system. 
 

logical operator

An operator used to compare logical expressions that returns a result of true or false. Examples of logical operators include less than (<), greater than (>), equal to (=), and not equal to (<>). 
 

logical query

The process of using mathematical expressions to select features from a geographic layer based on their attributes; for example, "select all polygons with an area greater than 16,000 units" or "select all street segments named Green Apple Run." 
 

logical selection

The process of using mathematical expressions to select features from a geographic layer based on their attributes; for example, "select all polygons with an area greater than 16,000 units" or "select all street segments named Green Apple Run." 
 

long transaction

An edit session on a feature dataset that may last from a few minutes to several months. Long transactions are managed by the ArcSDE versioning mechanism. 
 

longitude

The angular distance, usually expressed in degrees, minutes, and seconds, of the location of a point on the earth's surface east or west of an arbitrarily defined meridian (usually the Greenwich prime meridian). All lines of longitude are great circles that intersect the equator and pass through the North and South Poles. 
 

longitude of center

The longitude value that defines the center, and sometimes the origin, of a projection. 
 

longitude of origin

The longitude value that defines the origin of the x-coordinate values for a projection. 
 

long-range variation

In a spatial model, coarse-scale variation that is usually modeled as the trend. 
 

loop traverse

In surveying, a traverse that starts and ends with the same survey point. 
 

loose coupling

A relatively unstructured relationship between two software components or programs that work together to process data, which requires little overlap between methods, ontologies, class definitions, and so on. 
 

loosely coupled replication

A replication model that does not require the parent and child replicas to be directly connected for synchronization to occur. Loosely coupled replication is an asynchronous model, so edits made in one replica have no effect on other related replicas until synchronization. Synchronization can be executed manually, or it can be automated. 
 

lossless compression

Data compression that has the ability to store data without changing any of the values, but is only able to compress the data at a low ratio (typically 2:1 or 3:1). In GIS, lossless compression is often used to compress raster data when the pixel values of the raster will be used for analysis or deriving other data products. 
 

lossy compression

Data compression that provides high compression ratios (for example 10:1 to 100:1), but does not retain all the information in the data. In GIS, lossy compression is used to compress raster datasets that will be used as background images, but is not suitable for raster datasets used for analysis or deriving other data products. 
 

low-level language

A programming language that uses keywords and statements that are little more complex than the ones and zeros of machine language. Low-level language technically includes machine language, but more commonly refers to an assembly language that uses symbols to make machine instructions easier for programmers to read and understand. Each statement in assembly language represents a single command to the processor, affording the developer only a low level of abstraction in regard to mundane functions such as memory access and register storage, meaning such operations demand the developer's close attention. 
 

low-pass filter

A spatial filter that blocks high-frequency (shortwave) radiation, resulting in a smoother image. 
 

loxodrome

A complex curve on the earth's surface that crosses every meridian at the same oblique angle. A rhumb line path follows a single compass bearing; it is a straight line on a Mercator projection, or a logarithmic spiral on a polar projection. A rhumb line is not the shortest distance between two points on a sphere. 

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M

macro

A computer program, usually a text file, containing a sequence of commands that are executed as a single command. Macros are used to perform commonly used sequences of commands or complex operations. 
 

magnetic bearing

A bearing measured relative to magnetic north. 
 

magnetic declination

The angle between magnetic north and true north observed from a point on the earth. Magnetic declination varies from place to place, and changes over time, in response to changes in the earth's magnetic field. 
 

magnetic north

The direction from a point on the earth's surface following a great circle toward the magnetic north pole, indicated by the north-seeking end of a compass. 
 

magnetometer

An instrument used to measure variations in the strength and direction of the earth's magnetic field. 
 

Magnifier window

A secondary window in ArcMap data view that shows a magnified view of a small area without changing the map extent. Moving the Magnifier window around will not affect the current map display. 
 

maintenance license

A license that has a current maintenance contract with ESRI Customer Service. ESRI software users who have maintenance licenses are eligible for upgrade to the latest version of the software. 
 

maintenance renewal

The date a maintenance contract expires for a particular product. Multiple copies of the same product may expire on different dates. 
 

major axis

The longer axis of an ellipse or spheroid. 
 

majority resampling

A technique for resampling raster data in which the value of each cell in an output is calculated, most commonly using a 2x2 neighborhood of the input raster. Majority resampling does not create any new cell values, so it is useful for resampling categorical or integer data, such as land use, soil, or forest type. Majority resampling acts as a type of low-pass filter for discrete data, generalizing the data and filtering out anomalous data values. 
 

make permanent

In ArcGIS Spatial Analyst, an option that creates a permanent raster (one that is saved to disk) from a temporary result. 
 

managed raster catalog

A raster catalog in which the raster datasets are copied to a location assigned by a geodatabase. When a row is deleted from a managed raster catalog, the data is deleted as well. 
 

many-to-many relationship

An association between two linked or joined tables in which one record in the first table may correspond to many records in the second table, and vice versa. 
 

many-to-one relationship

An association between two linked or joined tables in which many records in the first table may correspond to a single record in the second table. 
 

map

A graphic representation of the spatial relationships of entities within an area. 
 

map algebra

A language that defines a syntax for combining map themes by applying mathematical operations and analytical functions to create new map themes. In a map algebra expression, the operators are a combination of mathematical, logical, or Boolean operators (+, >, AND, tan, and so on), and spatial analysis functions (slope, shortest path, spline, and so on), and the operands are spatial data and numbers. 
 

map annotation

In ArcGIS, text or graphics stored within the map data frame in an annotation group. Map annotation may be manually entered or generated from labels, and can be individually selected, positioned, and modified. 
 

map cache

A setting used in ArcMap that allows temporary storage of geodatabase or ArcIMS feature service features from a given map extent in the desktop computer's RAM, which may result in performance improvements in ArcMap for editing, feature rendering, and labeling. 
 

map collar

Any of the supporting objects or elements that help a reader interpret a map. Typical map surround elements include the title, legend, north arrow, scale bar, border, source information and other text, and inset maps. 
 

map configuration file

In ArcIMS, the file that contains the core site information. ArcIMS configuration files contain all the basic information about the content to be delivered, such as location of the data and layer symbology. Typically, a configuration file contains data that defines map content and has a file extension of .axl, but it can also be used to deliver metadata or route data (as .axl files) and to serve maps created in ArcMap (.mxd or .pmf files). Regardless of their type, configuration files contain content that the service registers to the ArcIMS spatial server and Web server for processing. 
 

map display

A graphic representation of a map on a computer screen. 
 

map document

In ArcMap, the file that contains one map, its layout, and its associated layers, tables, charts, and reports. Map documents can be printed or embedded in other documents. Map document files have a .mxd extension. 
 

map element

In digital cartography, a distinctly identifiable graphic or object in the map or page layout. For example, a map element can be a title, scale bar, legend, or other map-surround element. The map area itself can be considered a map element; or an object within the map can be referred to as a map element, such as a roads layer or a school symbol. 
 

map extent

The limit of the geographic area shown on a map, usually defined by a rectangle. In a dynamic map display, the map extent can be changed by zooming and panning. 
 

map feature

A representation of a real-world object on a map. 
 

map generalization

Decreasing the level of detail on a map so that it remains uncluttered when its scale is reduced. 
 

Map Image Web Service

A SOAP ArcWeb service that provides dynamic map content for Internet applications. With this service, users input a geographic extent and several optional items (such as themes, type of map, size of image, map annotation) and receive the location of an output image file. Map Image Web Service provides access to services from a variety of leading data publishers. 
 

map library

In ArcInfo Workstation Map Librarian, a collection of geographic data partitioned spatially as a set of tiles and thematically as a set of layers, indexed by location for rapid access. 
 

Map Production System

The cartographic component of the Production Line Tool Set (PLTS). MPS is designed to facilitate large-volume cartographic production by providing the ability to create dynamic map layouts, batch symbology, and enhanced cartographic editing tools. 
 

map projection

A method by which the curved surface of the earth is portrayed on a flat surface. This generally requires a systematic mathematical transformation of the earth's graticule of lines of longitude and latitude onto a plane. Some projections can be visualized as a transparent globe with a light bulb at its center (though not all projections emanate from the globe's center) casting lines of latitude and longitude onto a sheet of paper. Generally, the paper is either flat and placed tangent to the globe (a planar or azimuthal projection) or formed into a cone or cylinder and placed over the globe (cylindrical and conical projections). Every map projection distorts distance, area, shape, direction, or some combination thereof. 
 

map query

A statement or logical expression that selects geographic features based on location or spatial relationship. For example, a spatial query might find which points are contained within a polygon or set of polygons, find features within a specified distance of a feature, or find features that are adjacent to each other. 
 

map reading

The activity of viewing a map in a way that allows the viewer to make sense of or gain information from it. Map reading involves interpreting the meanings of codes and cartographic representations used on the map. 
 

map scale

The ratio or relationship between a distance or area on a map and the corresponding distance or area on the ground, commonly expressed as a fraction or ratio. A map scale of 1/100,000 or 1:100,000 means that one unit of measure on the map equals 100,000 of the same unit on the earth. 
 

map series

A collection of maps usually addressing a particular theme. 
 

map service

A type of Web service that generates maps. 
 

map sheet

A single map or chart in a map series, such as any one of the approximately 57,000 USGS 7.5-minute topographic maps of the United States and its territories. 
 

map style

An organized collection of predefined colors, symbols, properties of symbols, and map elements. Styles promote standardization and consistency in mapping products. 
 

map surround

Any of the supporting objects or elements that help a reader interpret a map. Typical map surround elements include the title, legend, north arrow, scale bar, border, source information and other text, and inset maps. 
 

map template

In ArcMap, a kind of map document that provides a quick way to create a new map. Templates can contain data, a custom interface, and a predefined layout that arranges map elements, such as north arrows, scale bars, and logos, on the virtual page. Map templates have a .mxt file extension. 
 

map topology

A temporary set of topological relationships between coincident parts of simple features on a map, used to edit shared parts of multiple features. 
 

map unit

The ground unit of measurement—for example, feet, miles, meters, or kilometers—in which coordinates of spatial data are stored. 
 

MapServer

An ArcGIS Server software component that provides programmatic access to the contents of a map document on disk and creates images of the map contents based on user requests. It is designed for use in building map-based Web services and Web applications using ArcGIS Server. 
 

MapTip

In ArcGIS, a user-assistance component that displays an on-screen description of a map feature when the mouse is paused over that feature. 
 

marginalia

Any of the supporting objects or elements that help a reader interpret a map. Typical map surround elements include the title, legend, north arrow, scale bar, border, source information and other text, and inset maps. 
 

marker symbol

A symbol used to represent a point location on a map. 
 

market area

A geographic zone containing the people who are likely to purchase a firm's goods or services. 
 

market penetration analysis

A process that determines the percentage of a market area being reached based on the number of customers within an area divided by the total population in that area. 
 

marshalling

The process that enables communication between a client object and server object in different apartments of the same process, between different processes, or between different processes on different machines by specifying how function calls and parameters are to be passed over these boundaries. 
 

mashup

In Internet mapping, the combination of content from more than one data source into one dynamic map service. 
 

mask

In digital cartography, a means of covering or hiding features on a map to enhance cartographic representation. For example, masking is often used to cover features behind text to make the text more readable. 
 

mass point

An irregularly distributed sample point, with an x-, y-, and z-value, used to build a triangulated irregular network (TIN). Ideally, mass points are chosen to capture the more important variations in the shape of the surface being modeled. 
 

master checkout version

In ArcGIS 9.1 and previous versions, the data version in the master geodatabase, created when data is checked out, that represents the state of the data at the time it was checked out. 
 

master geodatabase

In ArcGIS 9.1 and previous versions, a geodatabase from which data has been checked out. 
 

master site

In Business Analyst, the site of a known, well-performing business. 
 

match score

In geocoding, a value assigned to all potential candidates for an address match. The match score is based on how well the location found in the reference data matches with the address data being searched. 
 

matching

In geocoding, the process of linking a record, such as an address, to a set of reference data. The matched record in the reference data is used to determine the location of the input address. 
 

mathematical expression

A kind of expression that evaluates to a number which is then typically stored in a variable, a field on a table row, or a cell in a raster dataset. Mathematical expressions are generally part of an algebraic equation:Result = Expression[PropertyTax] = ( [LandValue] * 0.75 ) + ( [StructureValue] * 0.50 ) 
 

mathematical function

In ArcGIS Spatial Analyst, a function that applies a mathematical operation to the values of a single input raster. There are four groups of mathematical functions available: logarithmic, arithmetic, trigonometric, and powers. 
 

mathematical model

In Survey Analyst for field measurements, a set of relations between measurements and unknown coordinates. 
 

mathematical operator

The symbolic representation of a process or operation performed against one or more operands in an expression, such as "+" (plus, or addition) and ">" (greater than). When evaluated, operators return a value as their result. If multiple operators appear in an expression, they are evaluated in order of their operator precedence. 
 

matrix

A rectangular arrangement of data, usually numbers, in rows and columns. In computer science, a two-dimensional array is called a matrix. In GIS, matrices are used to store raster data. 
 

MAUP

Acronym for modifiable areal unit problem. A challenge that occurs during the spatial analysis of aggregated data in which the results differ when the same analysis is applied to the same data, but different aggregation schemes are used. MAUP takes two forms: the scale effect and the zone effect. The scale effect exhibits different results when the same analysis is applied to the same data, but changes the scale of the aggregation units. For example, analysis using data aggregated by county will differ from analysis using data aggregated by census tract. Often this difference in results is valid: each analysis asks a different question because each evaluates the data from a different perspective (different scale). The zone effect is observed when the scale of analysis is fixed, but the shape of the aggregation units is changed. For example, analysis using data aggregated into one-mile grid cells will differ from analysis using one-mile hexagon cells. The zone 
 

max extent

The maximum bounding rectangle (in x,y coordinates) of an on-screen map. Users cannot zoom out beyond the max extent. 
 

m-coordinate

In linear referencing, a measure value that is added to a line feature. M-values are used to measure the distance along a line feature from a vertex (a known location) to an event. 
 

mean

The average for a set of values, computed as the sum of all values divided by the number of values in the set. 
 

mean center

The location of a single x,y coordinate value that represents the average x-coordinate value and the average y-coordinate value of all features in a study area. 
 

mean sea level

The average height of the surface of the sea for all stages of the tide over a nineteen-year period, usually determined by averaging hourly height readings from a fixed level of reference. 
 

mean stationarity

In geostatistics, a property of a spatial process in which a spatial random variable has the same mean value at all locations. 
 

measure

In linear referencing, a value stored along a linear feature that represents a location relative to the beginning of the feature, or some point along it, rather than as an x,y coordinate. Measures are used to map events such as distance, time, or addresses along line features. 
 

measure location fields

In linear referencing, either one or two fields in a table that describe the position of an event along a route. 
 

measure value

In linear referencing, a measure value that is added to a line feature. M-values are used to measure the distance along a line feature from a vertex (a known location) to an event. 
 

measured grid

In cartography, any network of parallel and perpendicular lines superimposed on a map and used for reference. These grids are usually referred to by the map projection or coordinate system they represent, such as universal transverse Mercator grid. 
 

measurement

An observed numerical value that is an appraisal of size, extent, or amount according to a set criteria. 
 

measurement error

In surveying, the noise that is expected in every measurement. It occurs because the observer makes estimates and uses measuring equipment that is unpredictable in an environment that is also unpredictable. 
 

measurement residual

The difference between a measured quantity and its theoretical true value as determined during each iteration of a least-squares adjustment. 
 

median

The middle value of a set of values when they are ordered by rank. Half the values in a set are higher than the median, and half are lower. When there are two middle values (if the set has an even number of elements) the median is the mean of these two values. 
 

median center

A location representing the shortest total distance to all other features in a study area. 
 

medium-format printer

A printing device capable of producing an image on paper or other media sized between 15 and 35 inches (38 and 90 centimeters) wide. Medium-format printers typically use inkjet printing technology to print an image on a roll or sheet-fed media. While most large-format printers are large, free-standing units, most medium-format printers are small enough to fit on a desk. 
 

members

Refers collectively to the properties and methods, or functions, of an interface or class. 
 

memory cache

In ArcGlobe, the amount of system memory that the application will use. 
 

memory leak

In computer programming, the loss of computer memory that occurs when an application or component fails to free a section of computer memory when it has finished using it. During a memory leak, the section of memory allocated by one application or component may not be used by any other application. 
 

mental map

A person's perception of a place. A mental map may include the physical characteristics of a place, such as boundaries of a neighborhood, or the attributes of a place, such as a neighborhood's perceived unsafe areas. A mental map is primarily a psychological construct, although it may also be rendered as an actual map. 
 

menu

A list of available commands or operations displayed on a computer screen from which a user can make a selection. 
 

menu item

An item in a list of commands displayed on a menu. 
 

mereing

Establishing a boundary relative to ground features present at the time of a survey. 
 

merge policy

In geodatabases, rules that dictate what happens to the respective attributes of features that are merged together during editing in ArcMap. A merge policy can be set to assign a default value to the new attribute, summarize the values of the merged attributes, or create a weighted average from the merged attributes. 
 

merging

Combining features from multiple data sources of the same data type into a single, new dataset. 
 

meridian

A great circle on the earth that passes through the poles, often used synonymously with longitude. Meridians run north–south between the poles. By convention, meridians are labeled with positive numbers that ascend as one moves eastward from the prime meridian, and negative numbers as one moves westward from the prime meridian until the east and west hemispheres meet at the 180-degree line. Meridians can also, however, be labeled with all positive or negative numbers, including positive numbers increasing westward from the prime meridian. 
 

metabase

In Microsoft Internet Information Services (IIS), an XML file where the IIS configuration information is stored. 
 

metadata

Information that describes the content, quality, condition, origin, and other characteristics of data or other pieces of information. Metadata for spatial data may describe and document its subject matter; how, when, where, and by whom the data was collected; availability and distribution information; its projection, scale, resolution, and accuracy; and its reliability with regard to some standard. Metadata consists of properties and documentation. Properties are derived from the data source (for example, the coordinate system and projection of the data), while documentation is entered by a person (for example, keywords used to describe the data). 
 

metadata element

A unit of information within metadata, used to describe a particular characteristic of the data. 
 

Metadata Explorer

A Web application, developed using the ArcIMS Java Connector, that can be used to view metadata included in an ArcIMS metadata service. 
 

metadata profile

A modification of an existing metadata standard to adapt to data issues, cultural issues, or both. A profile is typically a subset of a base standard that tailors the metadata elements in the base standard to better describe the data to the community that uses it. Metadata profiles allow communities to follow a metadata standard, while at the same time enhancing the standard so that it is more appropriate for a particular use or locale. 
 

metadata server

A public ArcIMS virtual server that provides the capability to manage and search a central metadata repository. Data producers can publish their metadata to the repository while data consumers are able to search the repository to locate appropriate data. 
 

metadata service

A service that uses the spatial server metadata capabilities, allowing users to publish and share metadata documents over the Internet or an intranet. 
 

metes and bounds

A surveying method in which the limits of a parcel are identified as relative distances and bearings from landmarks. Metes and bounds surveying often resulted in irregularly shaped areas. 
 

method

In object-oriented programming, an action that an object is capable of performing. Objects that belong to the same class all have the same methods. For example, all Visual Basic form objects can execute a method called "Show and Hide." 
 

metropolitan statistical area

A geographic entity defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. A metropolitan statistical area is based on the concept of a core area with a large population nucleus, plus adjacent communities having a high degree of economic and social integration with that core area. According to the 1990 standards, to qualify as a metropolitan statistical area, the area must include at least one city or urbanized area with 50,000 or more inhabitants and a total metropolitan population of at least 100,000 (75,000 in New England). 
 

microdensitometer

A densitometer that can read densities in minute areas, used particularly for studying spectroscopic and astronomical images. 
 

micrometer

An instrument for measuring minute lengths or angles. 
 

micron

One millionth of a meter, represented by the symbol μm. Microns are used to measure wavelengths in the electromagnetic spectrum. 
 

micropolitan statistical area

A geographic region containing at least one urban area with a population between 10,000 and 50,000, defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. Micropolitan statistical areas include adjacent communities having a high degree of economic and social integration with the core area. 
 

MIDP

Acronym for Mobile Information Device Profile. A set of J2ME APIs for wireless devices. 
 

Military Analyst extension

An ArcGIS extension that optimizes the effectiveness of core ArcGIS as a toolset foundation for military planners and intelligence analysts. Military Analyst is COM-compliant and extensible with ArcObjects. 
 

MIL-STD-2525B Change 1

The military specification for common war fighting symbology; the U.S. military standard that provides guidelines and criteria for the development and display of standard C4I war fighting symbology. 
 

mimetic symbol

A symbol that imitates or closely resembles the thing it represents, such as an icon of a picnic table that represents a picnic area. 
 

min/max scale

The smallest and largest scales at which a layer is visible on a map. Scale ranges are used to prevent detailed layers from displaying when zoomed out and to prevent general layers from displaying when zoomed in. 
 

minimum bounding rectangle

A rectangle, oriented to the x- and y-axes, that bounds a geographic feature or a geographic dataset. It is specified by two coordinate pairs: xmin, ymin and xmax, ymax. 
 

minimum candidate score

In geocoding, the minimum score a potential match record requires to be considered a candidate. This value is adjustable on the Address Locator Properties dialog box. 
 

minimum map unit

For a given scale, the size in map units below which a narrow feature can be reasonably represented by a line and an area by a point. 
 

minimum match score

In geocoding, the minimum score a match candidate needs to be considered a match in batch geocoding. This value is adjustable on the Address Locator Properties dialog box. 
 

minor axis

The shorter axis of an ellipse or spheroid. 
 

minute

An angle equal to 1/60 of a degree of latitude or longitude and containing sixty seconds. 
 

misclosure

A discrepancy between existing coordinates and computed coordinates that occurs when the final point of a closed traverse has known coordinates and the final course of a traverse computes different coordinates for the same survey point. 
 

mixed list

In Survey Analyst for field measurements, one of two types of lists in the List page. The mixed list has a mixed set of rows that might have, for instance, survey points, coordinate geometry measurements, and a mix of different computations. 
 

mixed pixel

In remote sensing, a pixel whose digital number represents the average of several spectral classes within the area that it covers on the ground, each emitted or reflected by a different type of material. Mixed pixels are common along the edges of features. 
 

mobile toolkit

A J2ME-based toolkit for building mobile applications that use ArcWeb Services. 
 

model

An abstraction of reality used to represent objects, processes, or events. 
 

model generalization

The abstraction, reduction, and simplification of features and feature classes for deriving a simpler model of reality or decreasing stored data volumes. 
 

model parameter

In ArcGIS, a type of parameter exposed in a geoprocessing model that displays in a model's dialog box and allows for input. 
 

ModelBuilder

The interface used to build and edit geoprocessing models in ArcGIS. 
 

modifiable areal unit problem

A challenge that occurs during the spatial analysis of aggregated data in which the results differ when the same analysis is applied to the same data, but different aggregation schemes are used. MAUP takes two forms: the scale effect and the zone effect. The scale effect exhibits different results when the same analysis is applied to the same data, but changes the scale of the aggregation units. For example, analysis using data aggregated by county will differ from analysis using data aggregated by census tract. Often this difference in results is valid: each analysis asks a different question because each evaluates the data from a different perspective (different scale). The zone effect is observed when the scale of analysis is fixed, but the shape of the aggregation units is changed. For example, analysis using data aggregated into one-mile grid cells will differ from analysis using one-mile hexagon cells. The zone 
 

modifier

In MOLE, text or graphics that display around a symbol, or a value that changes the appearance of a symbol. In some military specifications, attributes are referred to as modifiers. 
 

MODIS

Acronym for moderate resolution imaging spectroradiometer. A bundle of remote-sensing equipment housed on two NASA (National Aeronautics and Space Administration) satellites, Terra and Aqua, in orbit around Earth. These two MODIS-equipped satellites constantly record multiple images of the globe in various wavelengths and resolutions, imaging the earth's entire surface in less than two days. 
 

MOLE

Acronym for Military Overlay Editor. An ESRI software application that allows users to create, display, and edit military symbology in their maps. 
 

monochromatic

Related to a single wavelength or a very narrow band of wavelengths. 
 

Monte Carlo method

An algorithm for computing solutions to problems that contain a large number of variables by performing iterations with different sets of random numbers until the best solution is found. The Monte Carlo method is usually applied to problems too complex for analysis by anything but a computer. 
 

monument

An object, such as a metal disk, permanently mounted in the landscape to denote a survey station. 
 

morphology

The structure of a surface. 
 

mosaic

A raster dataset composed of two or more merged raster datasets—for example, one image created by merging several individual images or photographs of adjacent areas. 
 

mouse mode

A way of using a digitizing tablet in which the digitizer puck behaves like a mouse; the puck is used to point to interface elements rather than to trace shapes on the surface of the digitizing tablet. 
 

MPS

Acronym for Map Production System. The cartographic component of the Production Line Tool Set (PLTS). MPS is designed to facilitate large-volume cartographic production by providing the ability to create dynamic map layouts, batch symbology, and enhanced cartographic editing tools. 
 

MSA

A geographic entity defined by the U.S. Office of Management and Budget for use by federal statistical agencies, including the U.S. Census Bureau. A metropolitan statistical area is based on the concept of a core area with a large population nucleus, plus adjacent communities having a high degree of economic and social integration with that core area. According to the 1990 standards, to qualify as a metropolitan statistical area, the area must include at least one city or urbanized area with 50,000 or more inhabitants and a total metropolitan population of at least 100,000 (75,000 in New England). 
 

MSDN

Acronym for Microsoft Developer Network. A set of services designed to help developers write applications using Microsoft products and technologies. 
 

MSS

A device carried on satellites and aircraft that records energy from multiple portions of the electromagnetic spectrum. 
 

MTA

Acronym for multiple threaded apartment. An apartment that can have multiple threads running. A process can only have one MTA. 
 

multichannel receiver

A receiver that tracks several satellites at a time, using one channel for each satellite. 
 

multidimensional data

Data that is comprised of multiple dimensions, such as space and time. For example, a temperature dataset could have dimensions of latitude, longitude, altitude, and time. 
 

multimodal network

A network in which two or more types of transportation modes (such as walking, riding a train, or driving a car) are modeled. In a network dataset, multiple connectivity groups are required to create a multimodal network. 
 

multipart feature

In ArcGIS, a digital representation of a place or thing that has more than one part but is defined as one feature because it references one set of attributes. In a layer of states, for example, the state of Hawaii could be considered a multipart feature because its separate geometric parts are classified as a single state. A multipart feature can be a point, line, or polygon. 
 

multipatch

In ArcGIS, a type of geometry comprised of planar three-dimensional rings and triangles, used in combination to model objects that occupy discrete area or volume in three-dimensional space. Multipatches may represent geometric objects like spheres and cubes, or real-world objects like buildings and trees. 
 

multipatch feature

In ArcGIS, a real-world geographic feature modeled using multipatch geometry. 
 

multipath error

Errors caused when a satellite signal reaches the receiver from two or more paths, one directly from the satellite and the others reflected from nearby buildings or other surfaces. Signals from satellites low on the horizon will produce more error. 
 

multiple regression

Regression in which the dependent variable is measured against two or more independent variables. 
 

Multiple Setup page

In the Survey Analyst for field measurements Survey Explorer, one of two types of setup pages. The Multiple Setup page is used for computations that process more than one instrument setup. 
 

multiple threaded apartment

An apartment that can have multiple threads running. A process can only have one MTA. 
 

multiplexing channel receiver

A receiver that tracks several satellite signals using a single channel. 
 

multipoint

In ArcGIS software, a geometric element defined by an unordered set of x,y coordinate pairs. 
 

multipoint feature

In ArcGIS software, a digital map feature that represents a place or thing that has neither area nor length at a given scale, and that is treated as a single object with multiple locations. For example, the entrances and exits to a prairie dog den might be represented as a multipoint feature. A multipoint feature is associated with a single record in an attribute table. 
 

multipoint feature class

A feature class that can store many points per shape or row, thereby saving storage space and improving read-write performance. 
 

multispectral

Related to two or more frequencies or wavelengths in the electromagnetic spectrum. 
 

multispectral image

An image created from several narrow spectral bands. 
 

multispectral scanner

A device carried on satellites and aircraft that records energy from multiple portions of the electromagnetic spectrum. 
 

multiuser geodatabase

A geodatabase managed in an RDBMS server by ArcSDE. Multiuser geodatabases can be very large and support multiple concurrent editors. They are supported on a variety of commercial RDBMS, including IBM DB2, IBM Informix, Oracle, Microsoft SQL Server, and PostgreSQL. 
 

multivariate analysis

Any statistical method for evaluating the relationship between two or more variables. 
 

multiversioned view

In ArcGIS and ArcSDE, a view that uses stored procedures and triggers to access a specified version of data in a single business table in the geodatabase. A multiversioned view includes all the records in the business table that have been selected and merged with records from the delta tables. The schema of a multiversioned view is identical to that of the business table on which it is based. 
 

m-value

In linear referencing, a measure value that is added to a line feature. M-values are used to measure the distance along a line feature from a vertex (a known location) to an event. 
 

MXD

In ArcMap, the file that contains one map, its layout, and its associated layers, tables, charts, and reports. Map documents can be printed or embedded in other documents. Map document files have a .mxd extension. 
 

My ArcWeb Locations

A feature in the ArcWeb Toolbar for ArcGIS that allows users to save and quickly access selected locations. 
 

My Output Data folder

A computer file that contains all the work done in Business Analyst: study areas; analyses; and customer, store, and extracted data. 
 

My services

The services that a user creates in Builder to use with ArcWeb Services. 
 

My Toolboxes folder

In ArcCatalog, a folder that contains nonsystem toolboxes created in the ArcToolbox window or directly in the My Toolboxes folder in the ArcCatalog Tree. The My Toolboxes folder points to a location on disk that can be changed in the Geoprocessing tab of the Options dialog box, accessible from the Tools menu. 

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N

NAD 1927

Acronym for North American Datum of 1927. The primary local horizontal geodetic datum and geographic coordinate system used to map the United States during the middle part of the twentieth century. NAD 1927 is referenced to the Clarke spheroid of 1866 and an origin point at Meades Ranch, Kansas. Features on USGS topographic maps, including the corners of 7.5-minute quadrangle maps, are referenced to NAD27. It is gradually being replaced by the North American Datum of 1983. 
 

NAD 1983

Acronym for North American Datum of 1983. A geocentric datum and graphic coordinate system based on the Geodetic Reference System 1980 ellipsoid (GRS80). Mainly used in North America, its measurements are obtained from both terrestrial and satellite data. 
 

nadir

In aerial photography, the point on the ground vertically beneath the perspective center of the camera lens. 
 

NAICS

Acronym for North American Industry Classification System. A system for classifying individual business locations by their types of economic activity. The statistics agencies of Canada, Mexico, and the United States collaborated on NAICS to standardize the industry statistics produced by the three countries. NAICS is used as an identification system by all federal statistical agencies, as well as many state and local agencies, trade associations, private businesses, and other organizations. NAICS replaced Standard Industrial Classification (SIC) codes in 1997. 
 

NaN

Acronym for not a number
 

N-ary association

A UML term that describes how two classes have a relationship with one or more other classes. In an N-ary association, instances of the classes in question usually exist together, but can exist on their own. For example, a three-way valve usually has one size of pipe coming in and two other sized pipes going out. Before the pipes and valve are connected into the water system they are separate parts; therefore, they have an N-ary association. 
 

National Geodetic Vertical Datum of 1929

The datum established in 1929 by the U.S. Coast and Geodetic Survey as the surface against which elevation data in the United States is referenced. 
 

National Spatial Data Infrastructure

A federally mandated framework of spatial data that refers to U.S. locations, as well as the means of distributing and using that data effectively. Developed and coordinated by the FGDC, the NSDI encompasses policies, standards, procedures, technology, and human resources for organizations to cooperatively produce and share geographic data. The NSDI is developed by the federal governments; state, local, and tribal governments; the academic community; and the private sector. 
 

natural breaks classification

A method of manual data classification that seeks to partition data into classes based on natural groups in the data distribution. Natural breaks occur in the histogram at the low points of valleys. Breaks are assigned in the order of the size of the valleys, with the largest valley being assigned the first natural break. 
 

natural neighbors

An interpolation method for multivariate data in a Delaunay triangulation. The value for an interpolation point is estimated using weighted values of the closest surrounding points in the triangulation. These points, the natural neighbors, are the ones the interpolation point would connect to if inserted into the triangulation. 
 

navigate

To interactively change the observer's or target's position using a tool designed for this purpose, such as the navigate or fly tool. There are three contexts in which a user can navigate: in a scene of ArcScene, in a preview of ArcCatalog, and in a globe of ArcGlobe. 
 

navigation

The combined mental and physical activities involved in traveling to a destination, often a distant or unfamiliar one. Navigation comprises wayfinding and locomotion. 
 

Navstar

The name of the U.S. Department of Defense's Global Positioning System (GPS). 
 

nearest neighbor resampling

A technique for resampling raster data in which the value of each cell in an output raster is calculated using the value of the nearest cell in an input raster. Nearest neighbor assignment does not change any of the values of cells from the input layer; for this reason it is often used to resample categorical or integer data (for example, land use, soil, or forest type), or radiometric values, such as those from remotely sensed images. 
 

neatline

The border delineating and defining the extent of geographic data on a map. It demarcates map units so that, depending on the map projection, the neatline does not always have 90-degree corners. In a properly made map, it is the most accurate element of the data; other map features may be moved slightly or exaggerated for generalization or readability, but the neatline is never adjusted. 
 

neighborhood

On a raster, an analysis boundary or processing window within which cell values affect calculations and outside which they do not. Filters are used mainly in cell-based analysis where the value of a center cell is changed to the mean, the sum, or some other function of all cell values inside the filter. A filter moves systematically across a raster until each cell has been processed. Filters can be of various shapes and sizes, but are most commonly three-cell by three-cell squares. 
 

neighborhood functions

Methods of defining new values for locations using the values of other locations within a given distance or direction. 
 

neighborhood statistics

The computation of an output raster where the output value at each cell location is a function of the value at that cell location and the values of the cells within a specified neighborhood around the cell. 
 

NetBeans IDE

An open-source development environment that supports all Java application types. 
 

network

An interconnected set of points and lines that represent possible routes from one location to another. For geometric networks, this consists of edge features, junction features, and the connectivity between them. For network datasets, this consists of edge, junction, and turn elements and the connectivity between them. For example, an interconnected set of lines representing a city streets layer is a network. 
 

network analysis

Any method of solving network problems such as traversability, rate of flow, or capacity, using network connectivity. 
 

network analysis class

In ArcGIS Network Analyst, a feature class or table containing network analysis objects that is stored within a network analysis layer. Network Analyst solvers read input from, and write output to, network analysis classes. 
 

network analysis layer

A composite layer that contains the properties and network analysis classes used in the analysis of a network problem, and the results of the analysis. 
 

network analysis object

In ArcGIS Network Analyst, a feature or row in a network analysis class. Network analysis objects are used as input and written as output during network analysis. A network location is a specific type of network analysis object that has a defined position on a network dataset. 
 

network ancillary role

An auxiliary or additional function performed by a junction feature within a geometric network. Junction features can act as sources or sinks for calculating flow direction. If a junction is a source or a sink, it is said to have an ancillary role in the network. 
 

network attribute

A type of attribute associated with a network element in a network dataset. Network attributes are used to help control flow through a network (similar to a weight in a geometric network). All network elements in a network dataset have the same set of attributes. There are four types of network attributes: cost, descriptor, hierarchy, and restriction. 
 

network dataset

A collection of topologically connected network elements (edges, junctions, and turns) that are derived from network sources, typically used to represent a linear network, such as a road or subway system. Each network element is associated with a collection of network attributes. Network datasets are typically used to model undirected flow systems. 
 

network element

A component in a network dataset: an edge, junction, or turn. All elements in a network dataset share the same set of network attributes. Network elements are used to model topological relationships in undirected flow networks such as traffic flow systems. Network elements are generated from point, line, and turn features. When the network dataset is built, point features become junctions, line features become edges, and turn features become turn elements. 
 

network feature

A component in a geometric network: an edge or a junction. Features in a geometric network are used to model topological relationships, typically in directed flow networks such as hydrologic or utility systems. Network features are generated from points and lines when the geometric network is built: point features become junctions, and line features become edges. 
 

network layer

A layer that references a network dataset. In a geodatabase, a network dataset is a collection of network elements (edges, junctions and turns) that are derived from network sources. 
 

network location

A geographic position in a network system. 
 

node

A connecting point in a geometric network, such as an intersection or interchange of a road network, confluence of streams in a hydrologic network, or switch in a power grid. 
 

network port

A number that is used to specify direct communication over a network to an Internet application. 
 

network solver

A function that performs network analysis based on a set of network data. 
 

network source

Feature classes in a geodatabase that are used to generate and define a network dataset. 
 

network trace

A function that performs network analysis on a geometric network. Specific kinds of network tracing include finding features that are connected, finding common ancestors, finding loops, tracing upstream, and tracing downstream. 
 

neural network

A computer architecture modeled after the human brain and designed to solve problems that human brains solve well, such as recognizing patterns and making predictions from past performance. Neural networks are composed of interconnected computer processors that calculate a number of weighted inputs to generate an output. For example, an output might be the approval or rejection of a credit application. This output would be based on several inputs, including the applicant's income, current debt, and credit history. Some of these inputs would count more than others; cumulatively, they would be compared to a threshold value that separates approvals from rejections. Neural networks "learn" to generate better outputs by adjusting the weights and thresholds applied to their inputs. 
 

new store analysis

A process that finds a potential location for a new store by calculating the centroid of a group of customers. 
 

NGVD 1929

The datum established in 1929 by the U.S. Coast and Geodetic Survey as the surface against which elevation data in the United States is referenced. 
 

NGVD29

The datum established in 1929 by the U.S. Coast and Geodetic Survey as the surface against which elevation data in the United States is referenced. 
 

NMEA

Acronym for National Marine and Electronics Association. A nonprofit association composed of manufacturers, distributors, dealers, educational institutions, and others interested in peripheral marine electronics occupations. The NMEA has created a standard that defines an electrical interface and data protocol for communications between marine instrumentation that has been adopted as an industry standard by the GPS industry. 
 

NoData

In raster data, the absence of a recorded value. NoData does not equate to a zero value. While the measure of a particular attribute in a cell may be zero, a NoData value indicates that no measurements have been taken for that cell at all. 
 

node

In a geodatabase, the point representing the beginning or ending point of an edge, topologically linked to all the edges that meet there. 
 

noise

In remote sensing, any disturbance in a frequency band. 
 

nominal data

Data divided into classes within which all elements are assumed to be equal to each other, and in which no class comes before another in sequence or importance; for example, a group of polygons colored to represent different soil types. 
 

nonsimple polygon

A polygon that violates topological integrity by crossing its own boundary (usually by making a small loop). 
 

nonspatial data

Data without inherently spatial qualities, such as attributes. 
 

normal distribution

A theoretical frequency distribution of a dataset in which the distribution of values can be graphically represented as a symmetrical bell curve. Normal distributions are typically characterized by a clustering of values near the mean, with few values departing radically from the mean. There are as many values on the left side of the curve as on the right, so the mean and median values for the distribution are the same. Sixty-eight percent of the values are plus or minus one standard deviation from the mean; 95 percent of the values are plus or minus two standard deviations; and 99 percent of the values are plus or minus three standard deviations. 
 

normal form

A set of guidelines for designing table and data structures in a relational database. When followed, normal form guidelines prevent data redundancy, increase database efficiency, and reduce consistency errors. A database is said to be in first normal form (1NF), second normal form (2NF), third normal form (3NF), and so on, depending on the level of normal form guidelines followed in its design. In practice, 3NF is commonly used, but higher levels are rarely used. 
 

normal probability distribution

A theoretical frequency distribution of a dataset in which the distribution of values can be graphically represented as a symmetrical bell curve. Normal distributions are typically characterized by a clustering of values near the mean, with few values departing radically from the mean. There are as many values on the left side of the curve as on the right, so the mean and median values for the distribution are the same. Sixty-eight percent of the values are plus or minus one standard deviation from the mean; 95 percent of the values are plus or minus two standard deviations; and 99 percent of the values are plus or minus three standard deviations. 
 

Normal template

The template that is automatically loaded in ArcMap and contains all the standard toolbar and command default settings. User interface customization that is saved in the Normal template is loaded each time ArcMap is launched. 
 

normalization

The process of organizing, analyzing, and cleaning data to increase efficiency for data use and sharing. Normalization usually includes data structuring and refinement, redundancy and error elimination, and standardization. 
 

North American Datum of 1927

The primary local horizontal geodetic datum and geographic coordinate system used to map the United States during the middle part of the twentieth century. NAD 1927 is referenced to the Clarke spheroid of 1866 and an origin point at Meades Ranch, Kansas. Features on USGS topographic maps, including the corners of 7.5-minute quadrangle maps, are referenced to NAD27. It is gradually being replaced by the North American Datum of 1983. 
 

North American Datum of 1983

A geocentric datum and graphic coordinate system based on the Geodetic Reference System 1980 ellipsoid (GRS80). Mainly used in North America, its measurements are obtained from both terrestrial and satellite data. 
 

North American Industry Classification System

A system for classifying individual business locations by their types of economic activity. The statistics agencies of Canada, Mexico, and the United States collaborated on NAICS to standardize the industry statistics produced by the three countries. NAICS is used as an identification system by all federal statistical agencies, as well as many state and local agencies, trade associations, private businesses, and other organizations. NAICS replaced Standard Industrial Classification (SIC) codes in 1997. 
 

north arrow

A map symbol that shows the direction of north on the map, thereby showing how the map is oriented. 
 

northing

The distance north of the origin that a point in a Cartesian coordinate system lies, measured in that system's units. 
 

NOTAM

Acronym for Notice to Airmen. An advisory bulletin containing information about the National Airspace System, typically time-sensitive information between publishing cycles, or corrections to published documents and charts. 
 

notice to airmen

An advisory bulletin containing information about the National Airspace System, typically time-sensitive information between publishing cycles, or corrections to published documents and charts. 
 

notice to mariners

A periodical update to existing nautical charts, issued by maritime authorities. 
 

NSDI

Acronym for National Spatial Data Infrastructure. A federally mandated framework of spatial data that refers to U.S. locations, as well as the means of distributing and using that data effectively. Developed and coordinated by the FGDC, the NSDI encompasses policies, standards, procedures, technology, and human resources for organizations to cooperatively produce and share geographic data. The NSDI is developed by the federal governments; state, local, and tribal governments; the academic community; and the private sector. 
 

NSDI Clearinghouse Network

A community of digital spatial data providers that maintain NSDI Clearinghouse Nodes as part of the U.S. National Spatial Data Infrastructure. 
 

NSDI Clearinghouse Node

An Internet server that hosts a collection of metadata and data maintained and stored on a computer server by a data provider. An NSDI Clearinghouse Node provides information about geographic data within the data provider's areas of responsibility. Nodes must host FGDC-compliant metadata and data and use a common access protocol. 
 

NTM

Acronym for Notice to Mariners. A periodical update to existing nautical charts, issued by maritime authorities. 
 

nugget

A parameter of a covariance or semivariogram model that represents independent error, measurement error, or microscale variation at spatial scales that are too fine to detect. The nugget effect is seen as a discontinuity at the origin of either the covariance or semivariogram model. 
 

null constraint

A DBMS-defined restriction specifying that a column cannot contain a null value. 
 

null hypothesis

A statement that essentially outlines an expected outcome when there is no pattern, no relationship, and/or no systematic cause or process at work; any observed differences are the result of random chance alone. The null hypothesis for a spatial pattern is typically that the features are randomly distributed across the study area. Significance tests help determine whether the null hypothesis should be accepted or rejected. 
 

null value

The absence of a recorded value for a field. A null value differs from a value of zero in that zero may represent the measure of an attribute, while a null value indicates that no measurement has been taken. 

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O

object

In GIS, a digital representation of a spatial or nonspatial entity. Objects usually belong to a class of objects with common attribute values and behaviors. 
 

object class

In a geodatabase, a collection of nonspatial data of the same type or class. While spatial objects (features) are stored in feature classes in a geodatabase, nonspatial objects are stored in object classes. 
 

Object Definition Language

Similar to Interface Definition Language, but used to define the objects contained in an object library. 
 

object library

A binary file that stores information about a logical collection of COM objects and their properties and methods in a form that is accessible to other applications at run time. Using a type library, an application or browser can determine which interfaces an object supports and invoke an object's interface methods. 
 

object model diagram

A graphical representation of the types in a library and their relationships. 
 

object pooling

The process of precreating a collection of instances of classes, such that the instances can be shared between multiple application sessions at the request level. Pooling objects allows the separation of potentially costly initialization and acquisition of resources from the actual work the object does. Pooled objects are used in a stateless manner. 
 

object view

A philosophical view of geographic space in which space is seen as empty except where occupied by objects. In this view, every spatial location is either something (an object) or nothing. 
 

ObjectID

In ArcGIS, a system-managed value that uniquely identifies a record or feature. 
 

object-oriented database

A data management structure that stores data as objects (instances of a class) instead of as rows and tables as in a relational database. 
 

object-oriented programming

A programming model in which related tasks, properties, and data structures are enclosed inside an object, and work is done when objects make requests and receive results from other objects. For example, a billing program may contain an object that maintains customer records. That object may pass information to another object that handles mailing statements, and another object that handles customer payments may ask it to update a customer record when a payment is received. 
 

oblate ellipsoid

An ellipsoid created by rotating an ellipse around its minor axis. The shape of the earth approximates an oblate ellipsoid with a flattening ratio of 1 to 298.257. 
 

oblate spheroid

An ellipsoid created by rotating an ellipse around its minor axis. The shape of the earth approximates an oblate ellipsoid with a flattening ratio of 1 to 298.257. 
 

oblique aspect

A planar or cylindrical projection whose point of tangency is neither on the equator nor at a pole. 
 

oblique photograph

An aerial photograph taken with the axis of the camera held at an angle between the horizontal plane of the ground and the vertical plane perpendicular to the ground. A low oblique image shows only the surface of the earth; a high oblique image includes the horizon. 
 

oblique projection

A planar or cylindrical projection whose point of tangency is neither on the equator nor at a pole. 
 

observer

In ArcScene and ArcGlobe, the position of the camera in a scene or globe. 
 

observer offset

In ArcScene and ArcGlobe, the height of the observer point above a surface used in analysis when calculating lines of sight and viewsheds. 
 

OCS

Acronym for output coordinate system. In ArcWeb Services, a user-defined map projection. 
 

OCX

Also known as an ActiveX control, an OLE custom control is contained in a file with the extension .ocx. The ArcGIS controls are ActiveX controls. 
 

OD cost matrix

In ArcGIS Network Analyst, a type of network analysis that computes a table containing the total impedance from each origin to each destination. Additionally, it ranks the destinations that each origin connects to in ascending order of the time it takes to travel from that origin to each destination. 
 

ODL

Acronym for Object Definition Language. Similar to Interface Definition Language, but used to define the objects contained in an object library. 
 

off-nadir

Any point not directly beneath a scanner's detectors, but rather off at an angle. 
 

offset

In cartography, the displacement or movement of features so that they do not overlap when displayed at a given scale. For example, a road can be offset from a river if the symbols are wide enough that they overlap. 
 

offset distance

The distance a label should be from the feature it labels. A label offset and a maximum label offset can be set for point features. Maximum label offsets are expressed as a percentage of the label offset. For line features, a label offset can be set from the line (similar to the label offset for point features) and along the line (which controls the position of the label relative to the ends of the line). Label offsets are not available for all label position options. 
 

OGC

Acronym for Open Geospatial Consortium. An international consortium of companies, government agencies, and universities participating in a consensus process to develop publicly available geospatial and location-based services. Interfaces and protocols defined by OpenGIS specifications support interoperability and seek to integrate geospatial technologies with wireless and location-based services. 
 

OGIS

Acronym for Open Geodata Interoperability Specification. A specification, developed by the Open Geospatial Consortium, Inc., to support interoperability of GIS in a heterogeneous computing environment. 
 

OID

In ArcGIS, a system-managed value that uniquely identifies a record or feature. 
 

OLB

Acronym for object library. A binary file that stores information about a logical collection of COM objects and their properties and methods in a form that is accessible to other applications at run time. Using a type library, an application or browser can determine which interfaces an object supports and invoke an object's interface methods. 
 

OLE

Acronym for Object Linking and Embedding. A protocol from Microsoft that allows the development of reusable objects that can be exchanged by multiple applications. Applications using OLE can create compound documents that link to data in other applications. The data can be edited from the document without switching between applications. 
 

OLE custom control

Also known as an ActiveX control, an OLE custom control is contained in a file with the extension .ocx. The ArcGIS controls are ActiveX controls. 
 

OLE DB provider

Object Linking and Embedding database provider. A tool conforming to the OLE standard for sharing data between applications. Each OLE DB provider communicates with and retrieves data from a different database, but a user can work with the data retrieved by any OLE DB provider in a similar way. 
 

OLE View

A utility, available as part of Microsoft Visual Studio, that can be used to view type information stored in a type library or object library or inside a DLL. 
 

on the fly

Assembled, created, presented, or calculated dynamically during a transaction such as a Web page search or data display query. 
 

on-demand cache

In ArcGlobe, a temporary layer cache that is placed on disk and built as areas of the layer are viewed. 
 

one-to-many relationship

An association between two linked or joined tables in which one record in the first table corresponds to many records in the second table. 
 

one-to-one relationship

An association between two linked or joined tables in which one record in the first table corresponds to only one record in the second table. 
 

one-way replication

A type of geodatabase replication that allows data changes to be sent multiple times from the parent replica to the child replica. In a one-way replication, the data in the parent replica is editable, and the data in the child replica is read-only. During synchronization, edits are applied directly to the child replica so that no conflicts occur. ArcSDE geodatabases are used to create one-way replicas. 
 

on-screen digitizing

Manual digitization by tracing a mouse over features displayed on a computer monitor, used as a method of vectorizing raster data. 
 

ontology

In computer science, a data model that represents a domain by detailing the entities that comprise it and the semantic relationships between them. Ontologies generally include individuals, classes, attributes and relations. 
 

Open Geodata Interoperability Specification

A specification, developed by the Open Geospatial Consortium, Inc., to support interoperability of GIS in a heterogeneous computing environment. 
 

Open Geospatial Consortium

An international consortium of companies, government agencies, and universities participating in a consensus process to develop publicly available geospatial and location-based services. Interfaces and protocols defined by OpenGIS specifications support interoperability and seek to integrate geospatial technologies with wireless and location-based services. 
 

open traverse

In surveying, a traverse that does not close back upon itself or on another point of known position. As such, it does not provide a means of checking for errors. 
 

OpenGIS Consortium

Acronym for Open Geospatial Consortium. An international consortium of companies, government agencies, and universities participating in a consensus process to develop publicly available geospatial and location-based services. Interfaces and protocols defined by OpenGIS specifications support interoperability and seek to integrate geospatial technologies with wireless and location-based services. 
 

OpenLS

Acronym for OpenGIS Location Services. A protocol, designed to work across the many different wireless networks and devices, that allows seamless access to multiple content repositories and service frameworks. 
 

operand

A data value or the symbolic representation of a data value in an expression. Operands may be numbers, character strings, functions, variables, parenthetical expressions in the body of a larger expression, and so on. Symbolic representations of operands, such as variables and functions, are evaluated before they are operated upon by the operators in the expression. For example, in the expression "1 + 2", the operands are 1 and 2, and are operated upon by the + (plus) operator, which adds the operands together and returns the value 3. 
 

operation codes

In surveying, an alphanumeric or numeric value included in an instrument vendor's data collector file format. Operation codes are used to describe such elements as new instrument setups and numeric values for horizontal angles, zenith angles, slope distance measurements, height of instrument, and height of target. These basic operation codes are supported in Survey Analyst for field measurements for the following formats: Geoserial Interface (GSI), TDS raw, TDS coordinate, Geodimeter, and Sokkia SDR. 
 

operator

The symbolic representation of a process or operation performed against one or more operands in an expression, such as "+" (plus, or addition) and ">" (greater than). When evaluated, operators return a value as their result. If multiple operators appear in an expression, they are evaluated in order of their operator precedence. 
 

operator precedence

The order in which operators are evaluated in an expression; operators with a higher precedence are evaluated before those with a lower precedence. If all operators in an expression have the same precedence, they are evaluated in the order in which they appear, from left to right. Parentheses may be used to override operator precedence; portions of an expression within parenthesis are evaluated first, and parenthetical expressions may be nested. 
 

optical center

The point on a rectangular map or image to which the eye is drawn. The visual center lies slightly (about 5 percent of the total height) above the geometric center of the page. 
 

optimization

The process of fine-tuning data, software, or processes to increase efficiency, improve performance, and produce the best possible results. 
 

Oracle

A database company that produces a relational database management system (also called Oracle), which allows data and other objects to be stored in tables. Oracle provides client/server access to data and uses indexes, sequences, and other database objects to facilitate rapid data creation, editing, and access. ESRI uses Oracle's RDBMS to store vector and raster data for use by ArcSDE. 
 

order

In ArcGIS Network Analyst, a network location used to determine routes in vehicle routing problem (VRP) analysis. Users can specify multiple orders. Orders may represent any combination of service locations or pickup/delivery locations to be visited along a route. 
 

order pair

In ArcGIS Network Analyst, an object used in vehicle routing problem (VRP) analysis. An order pair defines a relationship between two orders. The first order in the order pair represents a pickup which must then be delivered to the second order in the order pair on the same route. 
 

ordinal data

Data classified by comparative value; for example, a group of polygons colored lighter to darker to represent less to more densely populated areas. 
 

ordinary kriging

A kriging method in which the weights of the values sum to unity. It uses an average of a subset of neighboring points to produce a particular interpolation point. 
 

ordinate

In a rectangular coordinate system, the distance of the y-coordinate along a vertical axis from the horizontal or x-axis. For example, a point with the coordinates (7,3) has an ordinate of 3. 
 

Ordnance Survey

The national mapping and cartographic agency of the United Kingdom. Now a civilian organization, the Ordnance Survey is one of the world's largest producers of maps and was the first national mapping organization in the world to complete a large-scale program of digital mapping. 
 

orientation

An object's position or relationship in direction with reference to points of the compass. 
 

orientation of vertical labels

An option that controls whether a label can be placed in an upside-down or sideways position. A small angle prevents labels from switching their reading order in the labeling of nearly vertical lines. 
 

origin

A fixed reference point in a coordinate system from which all other points are calculated, usually represented by the coordinates (0,0) in a planar coordinate system and (0,0,0) in a three-dimensional system. The center of a projection is not always its origin. 
 

origin-destination cost matrix

In ArcGIS Network Analyst, a type of network analysis that computes a table containing the total impedance from each origin to each destination. Additionally, it ranks the destinations that each origin connects to in ascending order of the time it takes to travel from that origin to each destination. 
 

orthocorrection

The process of correcting the geometry of an image so that it appears as though each pixel were acquired from directly overhead. Orthorectification uses elevation data to correct terrain distortion in aerial or satellite imagery. 
 

orthogonal

Intersecting at right angles. 
 

orthogonal offset

A line that is perpendicular to another line at its point of tangency, often used to measure distance from a line to a separate point that does not lie along the original line. 
 

orthographic projection

A planar projection, tangent to the earth at one point, that views the earth's surface from a point approaching infinity, as if from deep space. 
 

orthographic view

In 3D Analyst, a perspective that allows viewing of data in a scene as a two-dimensional plane seen from above. There is no perspective foreshortening in orthographic view, so scale is constant across the entire display. 
 

orthomorphic projection

A projection that preserves the correct shapes of small areas. In a conformal projection, graticule lines intersect at 90-degree angles, and at any point on the map the scale is the same in all directions. A conformal projection maintains all angles at each point, including those between the intersections of arcs; therefore, the size of areas enclosed by many arcs may be greatly distorted. No map projection can preserve the shapes of larger regions. 
 

orthophotograph

An aerial photograph from which distortions owing to camera tilt and ground relief have been removed. An orthophotograph has the same scale throughout and can be used as a map. 
 

orthophotoquad

An orthophotograph that has been formatted as a USGS 1:24,000 topographic quadrangle with little or no cartographic enhancement. 
 

orthophotoscope

A photomechanical or optical-electronic device that creates an orthophotograph by removing geometric and relief distortion from an aerial photograph. 
 

orthorectification

The process of correcting the geometry of an image so that it appears as though each pixel were acquired from directly overhead. Orthorectification uses elevation data to correct terrain distortion in aerial or satellite imagery. 
 

outbound interface

An interface implemented by a class, on which that object can make calls to its clients; analogous to a callback mechanism. 
 

outlier

An unusual or extreme data value in a dataset. In data analysis, outliers can potentially have a strong effect on results and so must be analyzed carefully to determine if they represent valid or erroneous data. 
 

outline

The path that follows the boundary of an object. Outlines are also called strokes. 
 

outline vectorization

A vectorization method that generates lines along the borders of connected cells. It is typically used for vectorizing scanned land-use and vegetation maps. 
 

out-of-process

Within the process space of a client application, a component contained in an EXE is out-of-process; instantiated classes are loaded into the process space of the EXE in which they are defined rather than into that of the client. 
 

output coordinate system

In ArcWeb Services, a user-defined map projection. 
 

output data

Data that is the result of a computer, device, program, or process. 
 

output directory

In ArcIMS, the folder designated during installation to hold files being served to users for display in a browser. 
 

overflow list

A list of labels that could not be placed, generated during the process of converting labels to annotation. This list allows the manual placement or deletion of these labels. 
 

overlapping rings

A method of defining the rings in an analysis so that the values inside the rings are cumulative. For example, if you had an analysis with three concentric rings and 10 households in each, the total number of households for ring 1 would be 10, the total for ring 2 would be 20 (ring 1 + ring 2), and the total for ring 3 would be 30 (ring 1 + ring 2 + ring 3). 
 

overlay

A spatial operation in which two or more maps or layers registered to a common coordinate system are superimposed, either digitally or on a transparent material, for the purpose of showing the relationships between features that occupy the same geographic space. 
 

overlay events

In linear referencing, an operation that produces a route event table that is the logical intersection or union of two input route event tables. Event overlay is one way to perform line-on-line, line-on-point, and event point-on-point overlays. 
 

Overlay Wizard

In ArcGIS 8.3 and previous versions, an ArcToolbox wizard that uses overlay operations to create a new coverage by computing the geometric intersection of two coverages: an input coverage and an overlay coverage. 
 

overprinting

In cartography, portraying cartographic updates on a map by printing new or modified information over the original cartography, usually in a distinctive color. 
 

override

In network datasets, a type of junction connectivity policy in which the way junctions connect to other junctions is not based on the existing edge connectivity policy; junctions "override" the edge connectivity policy. 
 

overshoot

The portion of an arc digitized past its intersection with another arc. 
 

overview map

A generalized, smaller-scale map that shows the limits of another map's extent along with its surrounding area. 
 

overview terrain

Coarsest representation of the terrain dataset, intended for fast drawing at small scales. 
 

overview window

A secondary window in ArcMap data view that shows the full extent of the data, without changing the map extent. A red box in the window represents the current map extent. 
 

owner

In ArcWeb Services, the person responsible for creating and maintaining a layer or service. The owner determines who has access to the content and the content permissions. 

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P

packet

In Survey Analyst - Cadastral Editor, an XML stream or file containing the portion of the cadastral fabric that has been extracted by a cadastral fabric job for editing. 
 

page unit

The unit of measure, usually millimeters or inches, used to arrange map elements on a page for printing, as opposed to the coordinate system on the ground that the map represents. 
 

pan

To shift a map image relative to the display window without changing the viewing scale. 
 

pan sharpening

Sharpening a low-resolution multiband image by merging it with a high-resolution panchromatic image. 
 

panchromatic

Sensitive to light of all wavelengths in the visible spectrum. 
 

panchromatic image

A single band image generally displayed as shades of gray. 
 

panchromatic sharpening

Sharpening a low-resolution multiband image by merging it with a high-resolution panchromatic image. 
 

paneled map

A map spliced together from smaller maps of neighboring areas. 
 

parallax

The apparent shift in an object's position when it is viewed from two different angles. 
 

parallax bar

A stereoscope containing a micrometer for measuring the effects of parallax in a stereoscopic image. 
 

parallel

An imaginary east–west line encircling the earth, parallel to the equator and connecting all points of equal latitude. Also, the representation of this line on a globe or map. 
 

parallel processing

In computer data communications, a method of storing or sending data side by side, in groups of bits. Parallel data transmission is most often used for printer ports. 
 

parameter

One of the variables that define a specific instance of a map projection or a coordinate system. Parameters differ for each projection and can include central meridian, standard parallel, scale factor, or latitude of origin.&nbs