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Glossary
Position Uncertainty: The maximum distance from the
reported position to your actual position. This is reported on
the Oceanic Status page when in the oceanic/remote flight
phase, there is a RAIM alarm, and there are enough satellites
to calculate it. You are assured that your actual position is
within the displayed distance from your reported position.
Primary Oceanic/Remote Airspace Operations: The
NMC and it's GPS sensor continuously monitor GPS
satellite integrity and automatically remove a satellite from
position calculations if it is determined to be faulty in
accordance with FAA Notice N8110.60
PRN: Pseudo-Random Numbers used to uniquely identify
satellites. This is different than the SVN (Space Vehicle
Number) or the satellite serial number.
Radial: Any of the 360 magnetic courses from a VOR or
R
similar navigational aid, beginning at the navigational aid
and proceeding outward in a straight line.
RAIM: Receiver Autonomous Integrity Monitoring. A
method of predicting possible system accuracy errors that
may be caused by bad satellite data. The RAIM algorithm
requires that more satellites are available and usable than
required for a normal GPS position fix.
RAIM Alarm: A signal that, with RAIM available, RAIM
integrity for the current flight mode is exceeded.
RAIM Alarm Limit: The maximum RAIM integrity value
for the current phase of flight. The accuracy tolerance used
by the RAIM algorithm. The limit is set at 2 nm for Enroute
and Oceanic operations, 1 nm for Terminal operations, and
0.3 nm for Approach operations.
RAIM Availability, RAIM Detection: Availability of five
groups of four satellites, with adequate geometry, to provide RAIM.
RAIM Integrity: A measurement based on RAIM
calculations of the probability of error in the position
solution.
Range (RNG): The distance from the present position to a
destination waypoint.
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