gyrocompass

(-kum′pəs)

noun

a compass consisting of a motor-operated gyroscope whose rotating axis, kept in a horizontal plane, takes a position parallel to the axis of the earth's rotation and thus points to the geographical north pole instead of to the magnetic pole

See gyrocompass in American Heritage Dictionary 4

noun
A compass with a motorized gyroscope whose angular momentum interacts with the force produced by the earth's rotation to maintain a north-south orientation of the gyroscopic spin axis, thereby providing a stable directional reference.
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