Terms starting with G

GEO-LOCATIONAL ACCURACY

The degree to which the coordinates of points determined from a geospatially referenced image or dataset agree with the coordinates determined by ground survey or other independent, higher-accuracy means.

GEODESY

Science concerned with the measurement and mathematical description of the size and shape of the earth and its gravitational fields. Geodesy also includes the large-scale, extended surveys for determining positions and elevations of points, in which the size and shape of the earth must be taken into account. 

GEOGRAPHIC DATA

The locations and descriptions of geographic features. The composite of spatial data and descriptive data.

GEOGRAPHIC DATA SET

One of the seven geographic data types supported by ARC/INFO. Geographic data sets in ARC/INFO include coverage, grids, DBMS tables, tins, images, Lattices and CAD drawings.

GEOGRAPHIC DATABASE

A collection spatial data and related descriptive data organized for efficient storage and retirieval by many users.

GEOGRAPHIC FEATURE

A user - defined geographic phenomenon that can be modeled or represented using geographic data sets in ARC/INFO. Examples of geographic features include streets, sewer lines, Manhole cover, accidents, lot line and parcels.

GEOGRAPHIC INFORMATION SYSTEM (GIS)

An organized collection of computer hardware, software and digital geographic data designed to provide multiple layers of geographically-referenced information. GIS databases are used to efficiently capture, store, update, manipulate, analyze and display all forms of georectified information.

GEOID

Figure of the Earth visualized as a mean sea level surface extended continuously through the continents. It is a theoretically continuous surface that is perpendicular at every point to the direction of gravity (the plumbline).

GEORECTIFIED

The photogrammetric adjustment of one or more images relative to each other and to an absolute (fixed) ground reference system. An image or vector layer that is georectified is tied to a geographic reference system such that each pixel or point chosen can be identified by geographic coordinate (latitude and longitude).

GEOREFERENCED

A satellite image whose geographic coordinates have been matched with known, real-world coordinates.

GEOSPATIAL

Pertaining to the geographic location and characteristics of natural or constructed features and boundaries on, above or below the Earth’s surface, especially when referring to data that are geographic and spatial in nature.

GPS - GLOBAL POSITIONING SYSTEM

A satellite navigation system. A constellation of more than two dozen GPS satellites broadcasting precise timing signals by radio to electronic GPS receivers which allow them to accurately determine their location (longitude, latitude and altitude) in real time, day or night, in any weather, anywhere on Earth.

GRATICULE, GEOGRAPHIC

System of coordinates of latitude and longitude used to define the position of a point on the surface of the Earth with respect to the reference spheroid.

GRID

A fully intergrated grid (cell based) geoprocessing system for use with ARC/INFO. GRID supports a Map Algebra Spatial language that allows sophisticated spatial modelling and analysis.

A geographic data model representing information on an array of equally sized square cells arranged in rows and columns. Each grid cell is referenced by its geographic X, Y location.

GRID CELL

A discreetly uniform unit that represents a portion of the Earth, such as a sq. meter or sq. mile, Each grid cell has a value that corresponds to the feature or characteristic at the site such as a soil type, census tract or vegetation class.