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This is particularly important in high
latitudes, (such as Alaska, Labrador or
the North Sea), where the horizontal
component of the earth's magnetic field
(which is the portion the compass is trying
to detect) is very small relative to the
magnetic field of the vessel.
z The disadvantage of the magnetic
compass is that in very rough weather
with the vessel going to windward, it is
possible for the vessel motion to upset or
'tumble' the compass card, disabling the
autopilot.
z Because of the relative insensitivity
of the magnetic compass to both the
earth's and the vessel's vertical magnetic
fields, (due to its inertia), it IS
recommended for use at latitudes higher
than 50 degrees (North or South), AND
for use on steel vessels when the optional
quadrantal spheres are included.
z Locate and mount the compass in
a position which minimizes magnetic
interference. It should be at least three
feet away from such equipment as
radios, radars, depth sounders, and
engine instruments.
z The compass can be used as a
steering compass if desired. If the amount
of cable supplied is too short to reach the
rear of the autopilot, obtain an extra plug-
in length of cable from your dealer.
Cutting and splicing the compass
cable is NOT recommended.
z To reduce the possibility of the
card 'tumbling' in rough weather, mount
the compass as close as practical to the
centre of pitch. Mounting the compass
far forward under a bunk or similar
location is a poor choice for rough
weather performance.
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