GIS Glossary

Attribute: descriptive information about the properties of events, features, or entities associated with a location, such as the ownership of a parcel of land, or the population of a neighborhood, or the wind speed and direction over a point on the ground.

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

Cadastre: the map of ownership and boundaries of land parcels, often used to record ownership and assist in calculating taxes.

Cartography: the study and practice of making maps.

Datum: a definition of the origin, orientation, and scale of the coordinate system; usually a system of coordinate positions on a surface (horizontal datum) or heights above or below a surface (vertical datum).

Geocoding: assignment of alphanumeric codes or coordinates to geographically referenced data. Examples include the two-letter country codes, or the coordinates of a residence computed from its address. The end result is spatial data that can be displayed as features on a map.

Geodetic control: horizontal or vertical survey monuments that are primarily intended to serve as reference positions for other surveys or that serve to extend the national geodetic control networks.

Geographic information system (GIS): a digital database in which information is stored by its spatial coordinate system, which allows for data input, storage, retrieval, management, transformation, analysis, reporting, and other activities. GIS is often envisioned as a process as much as a physical entity for data.

Geospatial data: information that identifies the geographic location and characteristics of natural and constructed features and boundaries on Earth.

Global Positioning System (GPS): a navigation system supported by a constellation of 24 satellites owned and operated by the U.S. Department of Defense. The satellites transmit precise microwave signals that enable GPS receivers such as handheld devices or receivers installed in automobiles to determine their location, speed, and direction.

Hydrography: the charting and description of bodies of water.

LIDAR: acronym for Light Detection and Ranging, a remote sensing technique that uses laser pulses to determine elevation with high accuracy, usually from an aerial survey.

Map: a two-dimensional visual portrayal of geospatial data. The map is not the data itself.

Metadata: information about the quality, content, condition, and other characteristics of data. It may describe and document how, when, where, and by whom the data was collected, among other types of information.

Orthoimagery: An aerial photograph or image from which distortions resulting from camera tilt and ground relief have been removed. An orthophotograph or orthoimage has a uniform scale and can be used as a map.

Polygon: a feature in GIS used to represent areas (versus a point, or a line). A polygon is defined by the lines that make up its  boundary. On a map, the closed shape representing the area is defined by a connected sequence of coordinates, or x,y pairs.

Projection: a mathematical means of transferring information from the Earth’s three-dimensional, curved surface onto a two-dimensional map or computer screen.

Sources: Environmental Systems Research Institute, Inc., (ESRI), GIS Dictionary,  knowledgebase/Gisdictionary/browse; Urban and Regional Information Systems Association (URISA), GIS Glossary of Terms,