GIS Dictionary

1 [data models] 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. 2 [programming] … Read more

1 [ESRI software] 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 … Read more

[programming] A graphical representation of the types in a library and their relationships.

[programming] 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 … Read more

[cognition] 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) … Read more

[database structures] A data management structure that stores data as objects (instances of a class) instead of as rows and tables as in a relational database.

[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 … Read more

[ESRI software] In ArcGIS, a system-managed value that uniquely identifies a record or feature.

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.

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 … Read more

1 [map projections] A planar or cylindrical projection whose point of tangency is neither on the equator nor at a pole. 2 [map projections] A conic projection whose axis does … Read more

[ESRI software] In ArcScene and ArcGlobe, the position of the camera in a scene or globe.

[ESRI software] In ArcScene and ArcGlobe, the height of the observer point above a surface used in analysis when calculating lines of sight and viewsheds.

[programming] Acronym for Object Definition Language. Similar to Interface Definition Language, but used to define the objects contained in an object library.

[remote sensing] Any point not directly beneath a scanner’s detectors, but rather off at an angle.

1 [cartography] 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 … Read more

[standards] 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 … Read more

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.

[programming] 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 … Read more

[programming] 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 … Read more

[programming] 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.

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 … Read more

[ESRI software] 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 … Read more

[ESRI software] In ArcGlobe, a temporary layer cache that is placed on disk and built as areas of the layer are viewed.

[database structures] An association between two linked or joined tables in which one record in the first table corresponds to many records in the second table.

[database structures] 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.

[ESRI software] 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 … Read more

[ocial context of GIS] 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 … Read more

[surveying] 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 … Read more

[data sharing] 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 … Read more

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 … Read more

[surveying] 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 … Read more

[mathematics] 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, … Read more

[mathematics] 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 … Read more

[IS technology] The process of fine-tuning data, software, or processes to increase efficiency, improve performance, and produce the best possible results.

[computing] 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 … Read more

[ESRI software] 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 … Read more

[ESRI software] 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 … Read more

[data structures] Data classified by comparative value; for example, a group of polygons colored lighter to darker to represent less to more densely populated areas.

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.

[Euclidean geometry] 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 … Read more

[cartography] 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 … Read more

1 [geography] An object’s position or relationship in direction with reference to points of the compass. 2 [ESRI software] In Survey Analyst for field measurements, the method by which horizontal … Read more

[ESRI software] 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 … Read more

1 [coordinate systems] 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 … Read more

[ESRI software] 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 … Read more

[Euclidean geometry] Intersecting at right angles.

[Euclidean geometry] 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 … Read more

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.

[ESRI software] 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, … Read more

[aerial photography] An aerial photograph from which distortions owing to camera tilt and ground relief have been removed. An orthophoto has the same scale throughout and can be used as … Read more

An orthophotograph that has been formatted as a USGS 1:24,000 topographic quadrangle with little or no cartographic enhancement.

[aerial photography] A photomechanical or optical-electronic device that creates an orthophotograph by removing geometric and relief distortion from an aerial photograph.

[satellite imaging] 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 … Read more

[ESRI software] 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 … Read more

[programming] An interface implemented by a class, on which that object can make calls to its clients; analogous to a callback mechanism.

1 [statistics] 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 … Read more

[data models] The path that follows the boundary of an object. Outlines are also called strokes.

[data conversion] A vectorization method that generates lines along the borders of connected cells. It is typically used for vectorizing scanned land-use and vegetation maps.

[map display] 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 … Read more

[ESRI software] Acronym for output coordinate system. In ArcWeb Services, a user-defined map projection.

[modeling] Data that is the result of a computer, device, program, or process.

[ESRI software] In ArcIMS, the folder designated during installation to hold files being served to users for display in a browser.

[ESRI software] 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 … Read more

[spatial analysis] 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 … Read more

1 [analysisgeoprocessing] 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 … Read more

[ESRI software] 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 … Read more

1 [cartography] In cartography, portraying cartographic updates on a map by printing new or modified information over the original cartography, usually in a distinctive color. 2 [printing] In offset printing, … Read more

1 [ESRI software] 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; … Read more

[data structures] The portion of an arc digitized past its intersection with another arc.

[data management] In ArcGIS, a lower-resolution image created to increase display speed and reduce CPU usage when viewing a mosaicked image from a mosaic dataset.

[cartography] A generalized, smaller-scale map that shows the limits of another map’s extent along with its surrounding area.

[3D GIS] Coarsest representation of the terrain dataset, intended for fast drawing at small scales.

[ESRI software] 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 … Read more

1 [ESRI software] The person or organization responsible for creating and maintaining data or a map. The owner determines who has access to the content and the content permissions. 2 … Read more