Glossary of Terms - G


The process of adding geographic data to yield data or other field attributes either in real-time (on-the-go) or by post-processing, or the process of associating data points with specific locations on the earth’s surface.

Geostationary satellite

A satellite positioned approximately 35,700 km above the earth. At this altitude the satellite orbits as fast as the earth rotates on its axis, so it remains effectively stationary above a point on the earth. Satellite-based differential correction satellites are geostationary.

Geosynchronous satellite

A satellite moving west to east whose orbital period is equal to the earth’s rotational period. If the orbit is circular and lies in the plane of the equator, the satellite will remain over one point. Otherwise it will appear to make a figure eight once a day between the latitudes that correspond to its angle of inclination over the equator. The constellation for GPS is geosynchronous.

GIS (Geographic Information System)

A computer based system that is capable of collecting, managing and analyzing geographic spatial data. This capability includes storing and utilizing maps, displaying the results of data queries and conducting spatial analysis.

GLONASS (GLObal NAvigatsion Satellite System)

The Russian global navigation satellite system.

GNSS (Global Navigation Satellite System)

A generic term for satellite navigation systems that provide geo-spatial positioning with global coverage using time signals transmitted from satellites. The United States GPS and the Russian GLONASS are examples.

GPS (Global Positioning System)

Radionavigation facility which consists of a network of satellites and earth stations that are controlled by the U.S. Department of Defense to determine a radio receiver’s position in latitude, longitude and altitude.

GPS Antenna

A device that receives satellite signals from GPS satellites. On smaller hand held devices such as a smart phone the antenna is integrated into the device. For machine GPS systems, the antenna is often an external device mounted on top of the vehicle, away from the receiver.

Grid center method

Soil sampling method in which samples are taken from the center of a grid cell of a few acres. Also known as grid point sampling or point sampling.

Grid Sampling

The collection of samples from small, uniform-sized cells positioned systematically across a field.

Ground penetrating radar

A non-destructive system that uses pulses of electromagnetic radiation in the UHF and VHF bands to penetrate the ground and create an image of the subsurface from the reflected rays.

Ground referencing, ground truthing

Verification of the sensed surfaces that occurs simultaneously with remote sensing.