Aeronautical Terms beginning with G
G/S
Glide Slope
GAMA
General Aviation Manufacturers Association
Gateway Fix
A navigational aid or fix where an aircraft transitions between the domestic route structure and the oceanic route airspace.
GBT
Ground-Based Transmitter
GCA
Ground Controlled Approach
GCO
Ground Communication Outlet
GDP
Ground Delay Programs
GDPE
Ground Delay Program Enhancements
Geodetic Datum
The reference plane from which geodetic calculations are made. Or, according to ICAO Annex 15, the numerical or geometrical quantity or set of such quantities (mathematical model) that serves as a reference for computing other quantities in a specific geographic region such as the latitude and longitude of a point.
Glide slope (GS)
Part of the ILS that projects a radio beam upward at an angle of approximately 3° from the approach end of an instrument runway. The glide slope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.
Glide slope intercept altitude
The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.
Glidepath Angle (GPA)
The angular displacement of the vertical guidance path from a horizontal plane that passes through the reference datum point (RDP). This angle is published on approach charts (e.g., 3.00, 3.20, etc.). GPA is sometimes referred to as vertical path angle (VPA).
Glideslope (GS)
Part of the ILS that projects a radio beam upward at an angle of approximately 3° from the approach end of an instrument runway. The glideslope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.
Global landing system (GLS)
An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BRO VNAV).
Global Navigation Satellite System (GNSS)
An umbrella term adopted by the International Civil Aviation Organization (ICAO) to encompass any independent satellite navigation system used by a pilot to perform onboard position determinations from the satellite data.
Global positioning system (GPS)
Navigation system that uses satellite rather than ground-based transmitters for location information.
GLS
Global Navigation Satellite System Landing System
GNE
Gross Navigation Error
GNSS
Global Navigation Satellite Systems.
Goniometer
As used in radio frequency (RF) antenna systems, a direction-sensing device consisting of two fixed loops of wire oriented 90 from each other, which separately sense received signal strength and send those signals to two rotors (also oriented 90) in the sealed direction-indicating instrument. The rotors are attached to the direction-indicating needle of the instrument and rotated by a small motor until minimum magnetic field is sensed near the rotors.
GPS
Global Positioning System.
GPS Approach Overlay Program
An authorization for pilots to use GPS avionics under IFR for flying designated existing nonprecision instrument approach procedures, with the exception of LOC, LDA, and SDF procedures.
GPWS
Ground Proximity Warning System
Graveyard spiral
The illusion of the cessation of a turn while still in a prolonged, coordinated, constant rate turn, which can lead a disoriented pilot to a loss of control of the aircraft.
Great circle route
The shortest distance across the surface of a sphere (the Earth) between two points on the surface.
Ground Controlled Approach
A radar approach system operated from the ground by air traffic control personnel transmitting instructions to the pilot by radio. The approach may be conducted with surveillance radar (ASR) only or with both surveillance and precision approach radar (PAR). Usage of the term “GCA” by pilots is discouraged except when referring to a GCA facility. Pilots should specifically request a “PAR” approach when a precision radar approach is desired or request an “ASR” or “surveillance” approach when a nonprecision radar approach is desired.
Ground proximity warning system (GPWS)
A system designed to determine an aircrafts clearance above the Earth and provides limited predictability about aircraft position relative to rising terrain.
Groundspeed
Speed over the ground, either closing speed to the station or waypoint, or speed over the ground in whatever direction the aircraft is going at the moment, depending upon the navigation system used.
GS
Glide Slope.
GS
Groundspeed
GWPS
Ground Proximity Warning System.
GWS
Graphical Weather Service
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