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Magnetic North: The region, some distance from the
geographic north pole where the earth’s magnetic
lines concentrate. A magnetic compass points to the
magnetic north.
Magnetic Variation (Mag Var): The angle between
the magnetic and true north. At various points on the
earth it is different due to local magnetic disturbances.
It is shown on charts as isogonic lines marked with
degrees of variation, either east or west. These degrees
must be added to or subtracted from the true course to
get the magnetic course. (Easterly variations are
deducted, and westerly variations are added.) The
Apollo GX automatically sets magnetic variation to
0 degrees at positions above 70 degrees north or
south latitude. See Declination.
MAHP: Missed Approach Hold Point.
MAP: Missed Approach Point.
Map Datum: A mathematical model of the earth used
for the purpose of creating navigation charts and
maps. The Apollo GX uses the WGS-84 map datum.
MESA: Minimum En route Safe Altitude is the
highest MSA for every point between the aircraft
present position and the “TO” waypoint witha5nm
buffer around the course.
Meter (m): A metric distance measurement equal to
39.37 inches.
Minute: 1/60th of a degree.
MSA: Minimum Safe Altitude. The elevation of the
highest obstruction near the aircraft plus a 1,000 or
2,000 foot buffer added for safety. In
non-mountainous terrain, a 1,000 foot buffer is added.
In mountainous terrain, a 2,000 foot buffer is added.
The result is rounded to the nearest 100 feet.
15-7
Glossary