Gyrocompass

This article is about devices used on ships. For gyroscope used in aircraft, see Heading indicator.

Cutaway of an Anschütz gyrocompass

A gyrocompass repeater

A gyrocompass is a type of compass that does not use magnetism to point north. Normal compasses do not work around magnets, or big pieces of ferrous metal. Gyrocompasses do. This makes them very useful.

A gyrocompass is a non-magnetic compass based on a fast-spinning disc and the rotation of the Earth It automatically finds geographical direction.

Although one part of a gyrocompass is a gyroscope, these are not the same devices. A crucial ingredient is needed to turn a gyroscope into a gyrocompass, so it would automatically position to true north. This is some mechanism that applies torque whenever the compass's axis is not pointing north. Successful methods have two significant advantages over magnetic compasses:

• they find true north as determined by Earth's rotation, which is different from, and more useful than, magnetic north, and
• they are unaffected by ferromagnetic materials, such as ship's steel hull, which change the magnetic field