It is often part of a ships set of compasses, which also include a conventional gyrocompass and a magnetic compass.
en.wikipedia.org Magnetic compass adjustment and correction is one of the subjects in the examination curriculum for a shipmaster's certificate of competency.
en.wikipedia.org These included cast iron, the ploughshare, the stirrup, gunpowder, printing, the magnetic compass and clockwork escapements, most of which were thought at the time to be western inventions.
en.wikipedia.org The nature of the instrument and the alignment of the magnetic pole of the earth cause the magnetic compass to have several significant limitations when used for navigation.
en.wikipedia.org The instrument panel is fitted with an airspeed indicator, altimeter and vertical speed indicator, a magnetic compass, turn indicator, ignition switch and fuel pump.
en.wikipedia.org