II Morrow Inc. 920 User Manual
Page 92
concentrate. A magnetic compass points to the magnetic
north.
Mag Var (Magnetic Variation): The angle between the
magnetic and true north. It differs at various points on
the earth due to local magnetic disturbances. It is shown
on charts as isogonic lines marked with degrees of
variation, either east or west, degrees which must be
added to or subtracted from the true course to get the
magnetic course. Easterly variations are deducted, and
westerly variations are added.
Map Datum: A mathematical model of the earth used
for the purpose of creating navigation charts and maps.
Meter (m): A metric distance measurement equal to
39.37 inches.
Minute: 1/60th of a degree of a circle.
Nautical Mile (nm): A distance measurement equal to
6,076 feet, or 1.15 statute mile. One nautical mile is also
equal to one minute of latitude.
NDB
(Non-directional
Beacon):
A
low
frequency/medium frequency navigation aid sending
non-directional
signals
which
can
be
used
for
navigation.
G
5