GIS Glossary

From Wiki.GIS.com

Jump to:navigation, search

GIS Glossary

0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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. Referenced by: Performance Baseline History; WYSIWYG; Separation axiom; Address (geography); User interface; Hyperlink; Postal code; Public Land Survey System; Pixel; HTML; Hexadecimal; GLONASS.

Abbreviation Dictionary

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

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. Referenced by: Ordinate; Projective transformation; Sensitivity analysis; Cartesian coordinate system; Abscissa.

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. Referenced by: Global Positioning System; Chamberlin trimetric projection; Geographic information system; Digital elevation model; LIDAR Contour Mapping.

absolute coordinates

Coordinates that are referenced to the origin of a given coordinate system. Referenced by: Absolute coordinates; Real-time locating.

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. Referenced by: LIDAR; Radar; Image Interpretation; Ray tracing (graphics); Absorption (electromagnetic radiation); Spectrum; Spectroscopy; Sonar; Ground truth; Floating point; Electromagnetic radiation; Atomic clock.

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. Referenced by: Space; Variable (programming); Unified Modeling Language; Thread (computer science); Method (computer science); Computer file; Block (data storage); Adobe Flash; .NET Framework; Stone duality; Cloud computing; Business analyst.

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. Referenced by: Information Security; Access control list.

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. Referenced by: GIS Software Technology; Style sheet (web development); Page zooming; Spatial Decision Support System; Adobe Flash; Zoning; User interface; JavaScript; GLONASS; Cascading Style Sheets; Archive; Data model.

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. Referenced by: LIDAR; Mollweide projection; Radar; Albers equal-area conic projection; Erwin Raisz; Geographic Transformation; Spirit level; Terrain dataset; Feature class; Acronyms and Glossary; Performance Fundamentals; ArcGIS Survey Analyst.

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. Referenced by: Animation.

acknowledgement file

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

acknowledgement message

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

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. Referenced by: Information Security; Access control list.

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. Referenced by: Data Frame.

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. Referenced by: TeleCAD-GIS.

active remote sensing

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

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. Referenced by: Visual Basic; ASP.NET; Active Server Pages.

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. Referenced by: Contrast (vision); Edge enhancement; Acutance.

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. Referenced by: Information Security; Plug-in (computing); Fuzzy logic; Visual Basic; Instantatlas.

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. Referenced by: Update (SQL); Political geography; Point of interest; System Design Strategies Preface; Address Finder Web Service; Address data model; Address data format; Address data; Acronyms and Glossary; System Implementation; City of Rome; Capacity Planning Tool.

address data

Data that contains address information used for geocoding. Address data may consist of one individual address or a table containing many addresses. Referenced by: Address data model; Address data; Interoperability; Address Point; Mapping Services Agreement; Geocoding.

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. Referenced by: Address data model.

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. Referenced by: Postal code.

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. Referenced by: Address (geography); File Transfer Protocol.

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. Referenced by: ArcGIS Online; ESRI StreetMap Premium; ESRI; Geographic information system.

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. Referenced by: Address locator.

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. Referenced by: Web mapping; Geographic information system.

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. Referenced by: IP address.

address service

A service that can determine the x,y location of an address, and return the address of an x,y location. Referenced by: Address (geography).

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. Referenced by: GIS Data Administration; Adds table.

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. Referenced by: Acronyms and Glossary; City of Rome; Platform Performance; GIS Product Architecture; Software Performance; GIS Software Technology; Application Development Framework; Radio navigation; ESRI.

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. Referenced by: Topology; Dijkstra's algorithm; Topography; Geographic information system.

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. Referenced by: Equal Area Cylindrical; PostgreSQL; Political geography; WGS84; Figure of the Earth; World Geodetic System; WYSIWYG; Lossy compression; Unified Modeling Language; Tag (metadata); Style sheet (web development); Portable Network Graphics.

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). Referenced by: Stack (data structure); Abstract data type; JPEG.

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. Referenced by: Advanced Very High Resolution Radiometer; Geographic information system.

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. Referenced by: Bearing (navigation); Remote sensing; Azimuth; Superimposition; Cartography of Asia; Bird's-eye view; Georeference.

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. Referenced by: APP-6A; Earth.

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. Referenced by: Bézier curve; List of geometry topics; Orthographic projection; Helmert transformation; Cartesian coordinate system; Affine transformation; World file.

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. Referenced by: Spatial Decision Support System; Neural network; IP address; Hypertext Transfer Protocol; Property; Semantics; HTML; Digital image; Cascading Style Sheets; Common Gateway Interface; Artificial neural network; Abstraction.

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. Referenced by: Dbase; Site prospecting; IP address; SQL; Metadata; Dissolve; Artificial neural network; Spatial analysis; ONS coding system; Grid (spatial index); Mapscape BV; Modifiable areal unit problem.

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. Referenced by: Adobe Flex; APP-6A; ColdFusion; EarthBrowser; Virtual globe; Google Maps.

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. Referenced by: AIXM; GML Application Schemas.

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. Referenced by: Scripting language; Client (computing); Adobe Flash; .NET Framework; Cloud computing; User interface; JavaScript; Graphics Interchange Format; ColdFusion; ASP.NET; Yahoo! Maps; Bing Maps.

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. Referenced by: Absorption (electromagnetic radiation); Albedo; Planetary cartography.

alert

A message that calls attention to a notable situation or informs users of changes in the state of a monitored situation. Referenced by: Waypoint; Voxel; Password; Geofence; Digital; Atomic clock; Earth; Vehicle tracking system; Fuzzy locating system; SensorML; CrimeView; Federal Information Processing Standard state code.

algorithm

A mathematical procedure used to solve problems with a series of steps. Algorithms are usually encoded as a sequence of computer commands. Referenced by: Bézier curve; Quadtree; Z-order; Fréchet distance; Wizard (software); Travelling salesman problem; Solver (computer science); Software bug; Relational model; Regression analysis; Ray tracing (graphics); Probability distribution.

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. Referenced by: Adobe Flash; SQL; Remote sensing; Compiler; Aliasing; Otero Pedrayo; Autodesk.

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. Referenced by: Abstract data type; Jaggies; Wavelength; Texture mapping; Anisotropy; Aliasing; Distortion.

alidade

A peep sight mounted on a straightedge and used to measure direction. Referenced by: Sextant; Astrolabe; Alidade; Theodolite; Triangulation; Graphometer; Plane table; Quadrant (instrument); Circumferentor; Dioptra.

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. Referenced by: Buffering; Lossy compression; Variable (programming); Stack (data structure); Software bug; Information retrieval; Heap (data structure); File format; Concurrency (computer science); Computer file; Block (data storage); Bandwidth (computing).

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. Referenced by: Prediction; Sextant; Second; Longitude; GLONASS; Ephemeris; Global Positioning System; Insight Guides.

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. Referenced by: Relational model; Foreign key; Candidate key; Compound key; Alternate 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. Referenced by: Alternate name; Geocoding.

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. Referenced by: Radar; Point of interest; WGS84; World Geodetic System; Landsat 7; Aerial reconnaissance; List of geometry topics; Slope; Triangle; Latitude; Declination; Waypoint.

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. Referenced by: Geographic information system; ILWIS; Smallworld; AM/FM/GIS.

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. Referenced by: Interval (mathematics); Union (set theory); Relational model; Accuracy and precision; Bracket; Trilateration; JSON; SQL; Tessellation; Variogram; Cartesian coordinate system; First normal form.

American National Standards Institute

The private, nonprofit organization that develops U.S. industry standards through consensus and public review. Referenced by: SQL; Data model; ASCII; American National Standards Institute; Federal Information Processing Standard state code.

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. Referenced by: ASCII.

AML

Acronym for ARC Macro Language. A proprietary, high-level programming language created by ESRI for generating end-user applications in ArcInfo Workstation. Referenced by: Acronyms and Glossary; ArcGIS; ARC Macro Language; ArcInfo.

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. Referenced by: Anaglyph image; Stereoplotter.

analog

Represented continuously rather than in discrete steps; having value at any degree of precision. Referenced by: LIDAR; Quadtree; Lossy compression; Image resolution; Color depth; Bandwidth (computing); Raster scan; Parallel (geometry); Topological combinatorics; Fuzzy logic; Sperner's lemma; JPEG.

analog image

An image represented by continuous variation in tone, such as a photograph. Referenced by: Digital image processing.

analysis

A systematic examination of a problem or complex entity in order to provide new information from what is already known. Referenced by: LIDAR; GeoCommons; Radar; Buffer (GIS); Spatial (disambiguation); ArcGIS for AutoCAD; ESRI User Conference; Political geography; System Design Strategies Preface; Bézier curve; Beca GIS; Terrain dataset.

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. Referenced by: Regression analysis; Geostatistics; Spatial dependence; Goodness of fit; Analysis of variance; Analysis.

ancillary data

In digital image processing, data from sources other than remote sensing, used to assist in analysis and classification or to populate metadata. Referenced by: Data; Spatial analysis.

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. Referenced by: Turn (geometry).

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. Referenced by: Secant line; Angle; Dymaxion map; Bézier curve; ArcGIS Tracking Analyst; Vector graphics; Ray tracing (graphics); Portable Network Graphics; Object Linking and Embedding; Graphics tablet; Degree (angle); Chord (geometry).

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. Referenced by: Isotropy; Ellipse; Anisotropy.

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. Referenced by: Isotropy; Anisotropy.

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. Referenced by: Data Frame; Reference Scale; Feature class; Software Performance; Annotation feature class; Maplex 3.x; Maplex for ArcGIS; AutoCAD DXF; HTML; Cluster analysis; Annotation; Cartography.

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. Referenced by: Annotation feature class.

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. Referenced by: Analysis of variance; Analysis.

ANSI

Acronym for American National Standards Institute. The private, nonprofit organization that develops U.S. industry standards through consensus and public review. Referenced by: Primary key; .NET Framework; SQL; Visual Basic; Object-oriented programming; Serialization; Hexadecimal; Foreign key; Data model; C++; ASCII; American National Standards Institute.

Ant

An open-source, Java-based tool from the Apache Software Foundation that is used to manage the build procedure of applications. Referenced by: Travelling salesman problem; Data Definition Language; Shape; Cellular automaton; Cluster analysis; Emery Molyneux.

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. Referenced by: Human geography; Manifold; Antipodal point; Antipode; Antipodes; Map projection; David Harvey (geographer); Allan Pred; Neil Smith (geographer); Gillian Rose (geographer).

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. Referenced by: Terrain dataset.

apartment

In Microsoft's COM component programming model, a group of threads, working within a process, that work within the same context. Referenced by: Address (geography); Zoning; Census block; Contour line; Ingeborg de Beausacq.

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. Referenced by: Aphylactic projection.

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. Referenced by: AutoCAD; Acronyms and Glossary; City of Rome; Platform Performance; GIS Product Architecture; Network Communications; Software Performance; GIS Software Technology; ArcGIS API for Javascript; ArcGIS Online; ArcWeb Services APIs; Windows Registry.

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. Referenced by: Google Maps.

apogee

In an orbit path, the point at which the object in orbit is farthest from the center of the body being orbited. Referenced by: Polar orbit; Ephemeris.

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. Referenced by: Symbology; Military Overlay Editor; APP-6A.

appending

Adding features from multiple data sources of the same data type into an existing dataset. Referenced by: C++; Affine transformation; World file.

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. Referenced by: Bézier curve; Tissot's Indicatrix; Point (geometry); Plug-in (computing); Mercator projection; Slope; Neural network; Interpolation; Stereographic projection; Voronoi diagram; SWF; Surface.

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. Referenced by: GeoCommons; Network Design Guidelines; ESRI User Conference; Hydrography; System Design Strategies Preface; Performance Baseline History; Bézier curve; Design Web Format; AutoCAD; DWG; ArcSDE DBMS Configuration Alternatives; GIS System Architecture Evolution.

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. Referenced by: AutoCAD; GIS Product Architecture; ArcGIS API for Javascript; Plug-in (computing); Apache Axis; Cloud computing; Web server; Visual Basic; Relational database; Database; Application programming interface; List of GIS software.

application server

A computer program that receives user requests through a client application and returns results to the client. Referenced by: ArcSDE DBMS Configuration Alternatives; Acronyms and Glossary; City of Rome; Platform Performance; Information Security; Software Performance; ArcSDE direct connect; ArcIMS architecture; ArcIMS Application Server Connector; ArcIMS application server; Scripting language; Client (computing).

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. Referenced by: INFO; Performance Baseline History; Bézier curve; Network dataset; Feature class; Acronyms and Glossary; Platform Performance; GIS Software Technology; WGS84; Python; Curve; Shape theory (mathematics).

ARC Macro Language

A proprietary, high-level programming language created by ESRI for generating end-user applications in ArcInfo Workstation. Referenced by: Acronyms and Glossary; ARC Macro Language; ArcInfo.

arc second

An angle equal to one sixtieth of a minute of latitude or longitude. Referenced by: Google Earth.

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. Referenced by: GIS Product Architecture; Software Performance; GIS Software Technology; ArcGIS 3D Analyst; ArcGIS Online; ArcWeb Explorer; Address Manager; ArcWeb Services APIs; Map projection; ArcGIS; ArcGIS Explorer; ArcWeb Services.

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. Referenced by: ArcGIS Spatial Analyst; ArcGIS Extensions.

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. Referenced by: Metadata standards; ESRI User Conference; Erwin Raisz; System Design Strategies Preface; AutoCAD; ArcSDE DBMS Configuration Alternatives; GIS System Architecture Evolution; Acronyms and Glossary; System Implementation; City of Rome; Capacity Planning Tool; Platform Performance.

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. Referenced by: Metadata standards; Lossy compression; Portable Network Graphics; Image scanner; Serialization; Remote sensing; Archive; Data; Backup; Oceanography; Geomatics engineering; TransducerML.

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. Referenced by: GIS System Architecture Evolution; Acronyms and Glossary; Platform Performance; Information Security; GIS Product Architecture; Performance Fundamentals; Software Performance; GIS Software Technology; ArcSDE client application; ArcIMS Tasker; ArcIMS Service Administrator; ArcIMS architecture.

ArcIMS Administrator

The ArcIMS component that allows users to manage ArcIMS services, servers, virtual servers, and folders. Referenced by: ArcIMS Service Administrator; ArcIMS Application Server Connector; ArcIMS Designer.

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. Referenced by: ArcIMS architecture; ArcIMS Application Server Connector; ArcIMS application 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. Referenced by: ArcIMS Application Server Connector.

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. Referenced by: ArcIMS architecture.

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.). Referenced by: ArcIMS Author.

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. Referenced by: ArcIMS Application Server Connector; ArcIMS Designer.

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. Referenced by: ArcIMS architecture; ArcIMS Monitor.

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. Referenced by: ArcIMS Service Administrator.

ArcIMS Service Administrator

A Web-based administration application that allows users to manage ArcIMS services and ArcSDE services remotely. Referenced by: ArcIMS Service Administrator.

ArcIMS Tasker

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

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. Referenced by: ArcIMS application server.

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. Referenced by: Geographic Transformation; Acknowledgment message; Acronyms and Glossary; Platform Performance; Information Security; GIS Product Architecture; Network Communications; GIS Data Administration; GIS Software Technology; ArcObjects; MapServer; ArcGIS.

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. Referenced by: SDEHOME; System Design Strategies Preface; GlobalID; Version; Replication; Parent replica; Two-way replication; Geodatabase replication; Checkout/check-in replication; One-way replication; ArcSDE DBMS Configuration Alternatives; Feature class.

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. Referenced by: ArcSDE client application.

ArcSDE database server

In ArcCatalog, an instance of SQL Server Express used to store ArcSDE geodatabases. Referenced by: ArcSDE database server.

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. Referenced by: System Design Strategies Preface; Replication; Geodatabase replication; Checkout/check-in replication; ArcSDE DBMS Configuration Alternatives; Acronyms and Glossary; Platform Performance; GIS Product Architecture; GIS Data Administration; Software Performance; GIS Software Technology; ArcSDE direct connect.

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. Referenced by: ArcSDE system tables.

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. Referenced by: ArcToolbox; Python; ArcGIS Desktop; Topology; ArcGIS; ESRI.

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. Referenced by: ArcToolbox.

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. Referenced by: LIDAR.

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. Referenced by: ArcWeb Explorer.

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. Referenced by: GIS Software Technology; Data East; MapStudio; ArcWeb Explorer; Address Manager; ArcWeb Services APIs; ArcGIS Desktop; ArcGIS; ESRI; ArcWeb Services; Conservation Geoportal.

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. Referenced by: ArcXML; ArcIMS.

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. Referenced by: LIDAR; Update (SQL); Equidistant Cylindrical projection; Goode Homolosine projection; Gall Stereographic projection; Sinusoidal projection; Cassini projection; Butterfly World Map; Miller Cylindrical projection; Equidistant Conic projection; Loximuthal projection; Eckert VI projection.

area

A closed, two-dimensional shape defined by its boundary or by a contiguous set of raster cells. Referenced by: LIDAR; Miller Cylindrical projection; Loximuthal projection; Berghaus Star projection; Bonne projection; Craster Parabolic projection; Mollweide projection; Radar; Winkel Tripel; Equal Area Cylindrical; Albers equal-area conic projection; Lambert azimuthal equal-area projection.

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. Referenced by: Chart.

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. Referenced by: Clip; Terrain dataset; Image Interpretation; Spatial indexing; Local information systems; Cluster analysis; State Plane Coordinate System; Geography; Cultural geography; USGS DEM; Spot Image; Grlevelx.

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. Referenced by: Scale (map).

argument

In computing, a value or expression passed to a function, command, or program. Referenced by: Figure of the Earth; Space; Variable (programming); Stack (data structure); Information retrieval; Command (computing); BMP file format; Support (mathematics); Adobe Flash; Abstract data type; Differential GPS; Complex plane.

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. Referenced by: LIDAR; Radar; Acronyms and Glossary; GIS Product Architecture; GIS Data Administration; Dbase; GEOSS; Human geography; Lossy compression; Windows Registry; Vector graphics; Variable (programming).

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. Referenced by: Fuzzy logic; Self-organizing map; Computation; Cluster analysis; Automation; Artificial neural network.

ascending node

The point at which a satellite traveling south to north crosses the equator. Referenced by: GLONASS; Ecliptic; Global Positioning System.

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. Referenced by: Point of interest; Portable Network Graphics; File format; Character (computing); Bracket; AutoCAD DXF; Signature; Identifier; Graphics Interchange Format; Visual Basic; Plotter; Password.

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. Referenced by: Acronyms and Glossary; Personal IMS; .NET Framework; Web server; Visual Basic; Service provider; Dynamic-link library; Data dictionary; Delimiter; Application server; ColdFusion; ASP.NET.

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. Referenced by: .NET Framework; Visual Basic; Data dictionary; Delimiter; Application server; ColdFusion; ASP.NET; Active Server Pages; Bing Maps; TransCAD for the Web; Maptitude for the Web; Maptitude.

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. Referenced by: Lambert azimuthal equal-area projection; ArcGIS 3D Analyst; Image Interpretation; Curve; Variable (programming); Portable Network Graphics; Object Linking and Embedding; Index (database); Database normalization; Color depth; Manifold; Workflow.

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). Referenced by: Portable Network Graphics; JPEG; Graphics Interchange Format; Oblate spheroid; Equatorial bulge; Angular eccentricity; Centamap.

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. Referenced by: Rasterisation; .NET Framework; Bracket; Workflow; Quality assurance; Object-oriented programming; Plotter; Sextant; Property; Second; Hexadecimal; Dynamic-link library.

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. Referenced by: Symbology; Metadata standards; Erwin Raisz; Nevin Fenneman; Political geography; Image Interpretation; Aerial imagery; Human geography; Windows Registry; Row (database); Ray tracing (graphics); Local information systems.

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. Referenced by: Stereographic projection; Surveying; Navigation; Sextant; Longitude; Astrolabe; Alidade; Triangulation; Quadrant (instrument).

asynchronous

Not synchronous; that is, not occurring together or at the same time. Referenced by: PostgreSQL; GIS Data Administration; Downstream (computer science); Adobe Flex; Adobe Flash; .NET Framework; Standard Generalized Markup Language; Synchronization; Serialization; Distributed database; Cellular automaton; ColdFusion.

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. Referenced by: Equidistant Cylindrical projection; Goode Homolosine projection; Gall Stereographic projection; Sinusoidal projection; Cassini projection; Butterfly World Map; Miller Cylindrical projection; Equidistant Conic projection; Loximuthal projection; Eckert VI projection; Eckert V projection; Eckert II projection.

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. Referenced by: Navigation; Second; Atomic clock; Global Positioning System; GeaBios.

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. Referenced by: Rasterisation; Absorption (electromagnetic radiation); Band-pass filter; Backscatter; Distortion; Real-time location services; Fuzzy locating system.

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. Referenced by: Spatial analysis.

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. Referenced by: Spatial Selection; Attribute Query (Boolean Selection); Query Layer; Proportional Symbols; Graduated Symbols; Geometric Interval Classification; Quantile; Dot Density; Primary key; Feature class; Address data model; GIS Product Architecture.

attribute data

Tabular or textual data describing the geographic characteristics of features. Referenced by: Query Layer; GIS Product Architecture; GIS Data Administration; GIS Software Technology; Dbase; TAB Reader; ArcExplorer - Java Edition; File format; Georelational data model; Dissolve; Coverage data; MapInfo TAB format.

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. Referenced by: Attribute domain.

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. Referenced by: Spatial Selection; Attribute Query (Boolean Selection); Query; Geoprocessing.

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. Referenced by: Buffering; XTools Pro; Dissolve; GeoDA; Shapefile; Geographic information system; ILWIS.

attributes dialog box

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

attribution

The process of assigning attributes to features. Referenced by: World Geodetic System; United States Geological Survey; Authentication; Creative Commons Attribution-Share Alike License; GeoNames; ArcInfo; México Indígena; Geocoding.

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. Referenced by: Information Security; Signature; JSON; JavaScript; Intranet; HTTP Secure; Hypertext Transfer Protocol; SOAP; Password; Internet; File Transfer Protocol; Dongle.

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. Referenced by: System Implementation; Landsat 7; JavaScript; Intranet; SQL; File Transfer Protocol; Authentication; Vehicle tracking system; Fuzzy locating system; Virtual globe; Mapbender; Cherami.

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. Referenced by: Spatial (disambiguation); ArcGIS Geostatistical Analyst; Regression analysis; Feature extraction; Correlation; Autocorrelation; Anisotropy; Spatial analysis; Field (geography); GeoDA; TerraView; USGS DEM.

automated cartography

The process of making maps using computer systems that carry out many of the tasks associated with map production. Referenced by: Geographic information system.

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. Referenced by: AM/FM/GIS.

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. Referenced by: AutoCAD; ArcGIS Schematics; Python; Pixel Factory; Software deployment; Scripting language; Object Linking and Embedding; Client (computing); .NET Framework; Shortest path problem; ARCNET; Citrix Systems.

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. Referenced by: Radar; PostgreSQL; Base Map Layer; System Design Strategies Preface; System Implementation; City of Rome; Capacity Planning Tool; Platform Performance; Information Security; GIS Product Architecture; GIS Data Administration; GIS Software Technology.

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. Referenced by: Update (SQL); Principal meridian; River mile; Ingeborg de Beausacq; Joseph Nicollet; Adolph von Steinwehr; GSM localization; CrimeView; ArcGIS; MapBlast; Geographic information system.

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. Referenced by: Advanced Very High Resolution Radiometer; ERDAS IMAGINE; Geographic information system.

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. Referenced by: LIDAR; LIDAR; Gall Stereographic projection; Gall Stereographic projection; Lambert conformal conic projection; Lambert conformal conic projection; Prime Meridian; Prime Meridian; Platform Performance; Platform Performance; Performance Fundamentals; Performance Fundamentals.

axis

A line along which measurements are made in order to determine the coordinates of a location. Referenced by: LIDAR; LIDAR; Gall Stereographic projection; Gall Stereographic projection; Lambert conformal conic projection; Lambert conformal conic projection; Prime Meridian; Prime Meridian; Platform Performance; Platform Performance; Performance Fundamentals; Performance Fundamentals.

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. Referenced by: Loximuthal projection; Radar; Bearing (navigation); Polar coordinate system; Curvilinear coordinates; Declination; Stereographic projection; Spherical coordinate system; Remote sensing; Great circle; Gradient; Gnomonic projection.

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. Referenced by: Lambert azimuthal equal-area projection.