Selective Availability (SA): The degradation of
accuracy of GPS position fix data by the United
States Department of Defense for civilian use.
Space Vehicle (SV): A GPS satellite.
Statute Mile: A distance measurement equal to
5,280 feet or 0.87 of a nautical mile.
T
Three-dimensional (3D) Position Fix: A position
fix defined by latitude, longitude, and altitude.
Track (TRK): The imaginary line that the flight
path of an airplane makes over the earth.
Track Angle: The angle of your actual direction of
travel. Track angle is computed using the magnetic
variation at the Present Position.
Track
Angle
Error
(TAE):
The
difference
between the Desired Track and the Track Angle
(Dtk - Trk = Tae). Track angle is computed using
the magnetic variation at the Present Position.
TRU: True outside air temperature.
True North: Geographic north, at the earth’s north
pole.
Tower (TWR): Airport tower communication
frequency
U
UNICOM: The radio frequencies assigned to
aeronautical advisory stations for communication
with aircraft. Unicoms may provide such airport
information as active runway, wind direction and
velocity and other conditions of importance to
pilots.
Universal Time Coordinate (UTC): Greenwich
Mean Time, or the time at the Prime Meridian in
Greenwich, England. Also referred to as Zulu time.
Glossary of Navigation Terms
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