Aviation Maintenance Terms beginning with G

Galileo

A European satellite-based radio navigation system being developed that will provide a global positioning service.

Global Navigation Satellite System (GNSS)

The generic term for a satellite navigation system, such as GPS, that provides autonomous worldwide geo-spatial positioning and may include local or regional augmentations.

Global Positioning System (GPS)

A U.S. satellite-based radio navigation system that provides a global positioning service. The service provided by GPS for civil use is defined in the Global Positioning System Standard Positioning Service Performance Standard, 4th edition, dated September 2008, available at http://www.gps.gov/technical/ps/2008-SPS-performance- standard.pdf.

GNSS Time of Applicability

The time when the position output from the GNSS sensor is applicable.

GNSS Time of Measurement (TOM)

The time when the last GNSS signal used to determine the position arrives at the aircraft GNSS antenna.

Ground Speed

The magnitude of the horizontal velocity vector (see velocity). In these minimum operational performance standards (MOPS) it is always expressed relative to a frame of reference that is fixed with respect to the earth’s surface such as the WGS-84 ellipsoid.

Ground Track Angle

The direction of the horizontal velocity vector (see velocity) relative to the ground as noted in ground speed.