GIS Dictionary

[uncertainty] In GIS, a state of uncertainty in data classification that exists when an attribute applies to an indeterminate quality of an object or describes an indefinite quantity. For example, … Read more

[ESRI software] In coverages, the number of arcs that begin or end at a node.

[ESRI software] A table that lists the nodes in a data layer along with their valencies.

[ESRI software] A component of the PLTS knowledge base that contains the valid attribute combinations and rendering information for the features in a feature class. VVTs are used to symbolize … Read more

1 [software] The process, using formal methods, of evaluating a system or software component to determine whether it functions as expected and achieves the intended results. 2 [data quality] The … Read more

[data quality] A rule applied to objects in the geodatabase to ensure that their state is consistent with the system that the database is modeling. The geodatabase supports attribute, connectivity, … Read more

1 [mathematics] A measurable quantity that may be passed to a function. Values are either assigned or determined by calculation. 2 [graphics computing] The lightness or darkness of a color. … Read more

1 [mathematics] A symbol or placeholder that represents a changeable value or a value that has not yet been assigned. 2 [computing] A symbol or quantity that can represent any … Read more

[spatial analysis] A drawing technique for hiding part of one layer using another set of features. Variable depth masking allows a layer to be drawn with gaps at specific locations … Read more

[statistics] A numeric description of how values in a distribution vary or deviate from the mean. The larger the variance, the greater the dispersion of values around the mean. The … Read more

[surveying] In surveying, the symmetric 3×3 matrix that mathematically expresses the correlation between errors in coordinates x, y, and z.

[data structures] A data type that can contain any kind of data.

[spatial statistics use for geostatistics] A function of the distance and direction separating two locations that is used to quantify dependence. The variogram is defined as the variance of the … Read more

[spatial statistics use for geostatistics] The process of examining spatial dependence using a variogram; a set of procedures (as much art as science) for interpreting variograms.

[ESRI software] Acronym for value attribute table. A table containing attributes for a grid, including user-defined attributes, the values assigned to cells in the grid, and a count of the … Read more

[non-ESRI software] Acronym for Visual Basic Virtual Machine. The runtime environment used by Visual Basic code when it runs.

[data models] A coordinate-based data model that represents geographic features as points, lines, and polygons. Each point feature is represented as a single coordinate pair, while line and polygon features … Read more

[data models] A representation of the world using points, lines, and polygons. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and … Read more

[data conversion] The conversion of raster data (an array of cell values) to vector data (a series of points, lines, and polygons).

[software] GIS software settings that allow users to control the conversion of raster data to vector data. For example, vectorization settings may allow users to select which raster cells are … Read more

[ESRI software] An ArcScan tool that allows users to manually trace raster cells and generate features to be converted from raster to vector data.

[ESRI software] In ArcGIS Network Analyst, a type of network analysis for routing a fleet of vehicles to service a set of orders with the goal of minimizing some objective … Read more

[map design] A map scale that expresses the relationship between distance on the map and distance on the ground in words; for example, “One inch represents 20 miles.”

[software] The process, using formal methods, of evaluating a system or software component to determine whether it satisfies the requirements imposed at the start of development.

1 [database structures] In databases, an alternative state of the database that has an owner, a description, a permission (private, protected, or public), and a parent version. Versions are not … Read more

[database structures] The process of reconciling two versions of a dataset into a common version. If conflicting edits have been made in either of the merged versions, these conflicts are … Read more

[database structures] The process of updating a version of a dataset with changes made in another version. Using this technique, a version can remain up to date with changes even … Read more

[Euclidean geometry] One of a set of ordered x,y coordinate pairs that defines the shape of a line or polygon feature.

[coordinate systems] A reference system that defines the location of z-values relative to a surface. The surface may be gravity related, such as a geoid, or a more regular surface … Read more

[cartography] A multiplier applied uniformly to the z-values of a three-dimensional model to enhance the natural variations of its surface. Scenes may appear too flat when the range of x- … Read more

[geodesy] A geodetic datum for any extensive measurement system of heights on, above, or below the earth’s surface. Traditionally, a vertical geodetic datum defines zero height as the mean sea … Read more

[aerial photography] An aerial photograph taken with the camera lens pointed straight down.

[ESRI software] In ArcGIS, a parameter that offsets the z-origin from the surface of a vertical coordinate system. The vertical shift is similar in effect to the false easting or … Read more

1 [ESRI software] In ArcGIS, a way to see the contents of a selected item in the Catalog tree in ArcCatalog. 2 [ESRI software] In ArcView 3, one of the … Read more

[software] In ArcGlobe and 3D Analyst, an additional window that allows a user to view 3D data in a scene from another angle. Users can have multiple viewers in a … Read more

[3D analysis] The locations visible from one or more specified points or lines. Viewshed maps are useful for such applications as finding well-exposed places for communication towers, or hidden places … Read more

[Internet] A directory name, used in a URL, that corresponds to a real or actual directory on a Web server.

[ESRI software] The map page as seen in layout view in ArcMap.

[ESRI software] The current extent of a map document in ArcGIS. The virtual study area never has a boundary.

[computing] A logical table in a database that stores a pointer to the data rather than the data itself.

[ESRI software] A minimum and maximum value that a map scale must fall between in order for the map layers to be displayed.

[non-ESRI software] A programming language developed by Microsoft based on an object-oriented form of the BASIC language and intended for application development. Visual Basic runs on Microsoft Windows platforms.

[non-ESRI software] The embedded programming environment for automating, customizing, and extending ESRI applications, such as ArcMap and ArcCatalog. It offers the same tools as Visual Basic in the context of … Read more

[programming] A Microsoft implementation of the C++ programming language which is part of Microsoft’s Visual Studio Development environment, used to compile and develop Windows software.

[map design] 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 … Read more

[map design] The presentation of features on a map in a way that implies relative importance, usually achieved with visual contrast.

[visualization] The representation of data in a viewable medium or format. In GIS, visualization is used to organize spatial data and related information into layers that can be analyzed or … Read more

[standards] Acronym for Vector Map. A vector-based data product in vector product format (VPF) at several scales divided into groups, referred to as levels. For example, VMap Level 1 includes … Read more

1 [data analysis] In a TIN, the space (measured in cubic units) between a TIN surface and a plane at a specified elevation. Volume may be calculated above or below … Read more

[Euclidean geometry] 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. … Read more

[graphics computing] A three-dimensional pixel used to display and rotate three-dimensional images.

[data structures] Acronym for Vector Product Format. A vendor-neutral data format used to structure, store, and access geographic data according to a defined standard.

Acronym for Vector Product Format. A vendor-neutral data format used to structure, store, and access geographic data according to a defined standard.

[ESRI software] A layer that references a set of VPF data. VPF data is a standard format, structure, and organization for large geographic databases that are based on a georelational … Read more

[programming] The fastest form of early binding, during which client code that uses a COM object (such as Visual Basic) binds to a method by indexing to a virtual function … Read more