A gyroscope that is driven continuously so that it can be used as a nonmagnetic compass. When the earth rotates the gyroscope experiences no torque if its spin axis is parallel to the earth's axis; if these axes are not parallel, however, the gyroscope experiences a sequence of restoring torques that tend to make it align itself with the earth's axis. The gyrocompass is therefore an accurate north-seeking device that is uninfluenced by metallic or magnetic objects and it is more consistent than the magnetic compass. It is widely used on ships, aircraft, missiles, etc.
From: gyrocompass in A Dictionary of Physics »
Subjects: Science and technology — Physics