Geographic Information System (GIS) Terms & Definitions Glossary

GIS is a system for collecting, managing, and analyzing geographical data. The GIS Glossary of Terms and Definitions contains a listing of terms that are commonly used and associated with GIS technology throughout all industries.  If you have any terms that you think should be included please submit them through our contact us page and select “Other” in the dropdown.

While this list may not be comprehensive, it’s a good beginning on the fundamentals.





Abscissa:  The separation between the vertical or y-axis and the x-coordinate along a horizontal axis in a rectangular coordinate system.

American Standard Code for Information Interchange (ASCII):  This file format stores and processes data using a range of numbers between 0 and 255.

Area:  A description of a polygon’s size or contents.

Aspect:  Aspect is the direction of the slope of a terrain surface measured clockwise starting north as 0° to 360° north again with flat areas given a value of -1 or 0 degrees.

Asset MappingGives users a better and quicker visual view of where assets are located along with the important information associated with every asset.




Basemap: A georeferenced is a background image that serves as a point of reference on a map providing an aesthetic appeal. This cannot be edited.

Benchmark:  A benchmark is a precisely surveyed site that is typically marked with a metal disk in the ground. Survey markers, geodetic marks, and control stations are other names for benchmarks.

Buffer:  The buffer tool’s proximity function builds a polygon around a chosen feature or combination of features at a predetermined distance.




Cartography:  The art, science, and study of depicting physical objects on maps by communicating spatial information

Class:  Data are grouped according to the range of values of a specific characteristic or attribute.

Coordinates: Coordinates are pairs (X, Y) or triplets (X, Y, Z) of values that are used to represent points and features on a two and three-dimensional surface.




Data:  Data is a group of facts, ideas, or instructions that have been formalized and are ready for processing by machines or by people. Generally used in the GIS field as a reference to all spatial information.

Data Field: A column in a data table.

Data Set:  A dataset is a collection of GIS data tables that are typically connected by a common system. The Storm dataset, which includes manholes, lines, catch basins, detention basins, culverts, ditches, swales, and flow direction associated with stormwater runoff, serves as an example. The term “dataset” is also occasionally used to refer to an entire data collection.

Database Management System (DBMS):  A group of technologies that make it possible to enter, store, output, organize and utilize data while serving as an interface between users and databases.

Datum:  A datum offers a point of comparison for measuring locations on the earth’s surface. It defines where latitude and longitude lines come from and how they are oriented.

Digital Line Graph (DLG:  The United States Geological Survey (USGS) uses and disseminates the digital line graph (DLG) data format to represent geographic elements such as topography, hydrography, transportation, and man-made landmarks.

Documentation (GIS) Documentation in the context of GIS refers to a feature class, dataset, database, and/or associated processes. This might be demonstrated, for instance, by listing and defining feature attributes. Although metadata offers more in-depth information about geodata, it is frequently referred to as documentation.




Entity:  Entities are used to represent world points, lines, or polygonal elements in a specific geographic location. Examples include hospitals, fire hydrants, roads, state borders, rivers, lakes, etc.




Feature:  A feature is a cartographic point, line, or polygon object with a spatial location in the real-world landscape that can be used in a GIS for storage, visualization, and analysis.

Field (Attribute Table): Characteristics used to describe each feature in a geographic data set which is usually viewed as columns in a table.




Geocoding:  This is the process of turning a description of a location, such as its physical address, into a precise location on a map, namely, a pair of coordinates. 

Geographic Information Systems (GIS):  Is a computer-based tool that analyzes, stores, manipulates, and visualizes geographic information on a map, good for finding spatial patterns, relationships, and trends.

Geographic Information Systems (GIS Asst Mapping): Integrates Geographic Information System (GIS) technology, and Enhanced Interactive Image Mapping to further enhance the accuracy in tracking and mapping of assets and work orders.

Geographic Information Systems (GIS) “Lite”:  A general term that is frequently used to describe GIS products that are easier to use and have fewer features. GIS Lite tools are typically web-based and don’t need any specialized knowledge.

Geodatabase:  A database or file structure used primarily to store, query, and manipulate spatial data. Geodatabases store geometry, a spatial reference system, attributes, and behavioral use data.

Georeference:  An action that involves aligning an image (such as an aerial shot) to a recognized coordinate system so that it can be viewed and examined with other geographical data.




Hydrography:  A term used to describe how lakes, rivers, and streams are represented geographically.

Horizontal A network of known horizontal geographic positions that are oriented along plane coordinate axes, meridians, or other lines of orientation.




Infrastructure:  Refers to the roads, cables, wires, pipes, bridges, canals, reservoirs, and sewers that support the economy and society.

Isogonic lineLine joining points on the earth’s surface having equal magnetic declination as of a given date.

Internet GIS:  Is a network-based geographic information service that utilizes both wired and wireless Internet to access and distribute geographic information, spatial analytical tools, and GIS web services






Kriging:  Is a statistical interpolation method that uses standard location values to interpolate values at unknown locations and also estimates standard error and uncertainty.




Latitude: Latitude is a term used to describe the north-south coordinates of the earth’s locations. It ranges from 0° at the equator to 90° (North or South) at the poles.

Layer:  In any digital map setting, a layer is the visual representation of a geographic dataset. A layer is similar to a legend item on a paper map containing groups of points, lines, or area (polygon) features representing a particular class or type of real-world entities such as customers, streets, or postal codes.

Longitude:  A coordinate term with values from 0 to 180 degrees east and west.




Map:  A visual representation of phenomena with a global distribution. Symbols or signs may be used to represent the information being shown.

Map Legend:  A pictorial representation of the symbology used in a map that explains to the reader what each polygon, line, point, and grid cell on the map stands for.

Meridian:  Meridians are lines of longitude that vary in east-west directions ranging from 0° to +180° east and −180° west.

Metadata: Information on the origin, accuracy, date, abstract, coordinate system, and other attributes of the data.




Nominal Scale:  A graphic that shows the position of the north on a map.

North Arrow: The graphical representation of which direction north is on the map.




Object-Based Image Analysis (OBIA): This allows users to segment images and classify them as a set of regions and not anymore as a set of pixels.




Parallax: Measures the apparent shift in an object’s position when it is viewed from two different angles.

Polygon:  A polygon is a set of connected, closed lines that delineates a region’s perimeter and areas, such as a lake or a forest, or the border of a nation.




QGIS:  A free and open-source (and fully featured) GIS platform.

Query:  A search of spatial or tabular data based on user-defined criteria, producing a subset of chosen records.




Raster Data:  A data model used in GIS that typically consists of square or rectangular grid cells that are arranged in rows and columns.

Remote Sensing:  Remote sensing is the art and science of making measurements of the earth using sensors on airplanes or satellites.  




Scale:  The ratio or fraction between the distance on a map, chart, or photograph and the corresponding distance in the real world.

Scale Bar A map element that shows the scale of a map graphically.

Set:  A group of features and their data.

Shapefile:  A simple format for storing the geometric location and attribute information of geographic features

Slope:  Measured in degrees or percent slope, elevation change, or steepness change with relation to location change raft.

Spatial Data:   A spatial relationship that links features geographically with a table by a unique identifier.

Spherical Coordinates:  A system based on a sphere defined by two angles of rotation in orthogonal planes such as latitudes and longitudes in a geographic coordinate system.




Thematic Layer:  A distinct spatial entity in a data layer that is usually delineated as points, lines, and polygons.

Topography: The study of the land surface is known as topography. It creates the groundwork for a landscape in particular. For instance, topography describes the surface’s mountains, valleys, rivers, or craters.

Tabular Data:  Descriptive information, usually alphanumeric, that is stored in rows and columns in a database and can be linked to spatial data.




United States Geological Survey (USGS) Is a United States agency responsible for studying the landscape of the United States.   

Universal Transverse Mercator (UTM)Is a standard set of map projections with a central meridian for each six-degree of longitude in width.




Vector Data Model:  Common GIS feature representation of spatial information based on defining coordinates and attribute information in points, polylines, and polygons.




Web GIS Allows the sharing of GIS data, maps, and spatial processing across private and public computer networks.








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