Gyrocompass is a mechanical device that determines direction. It is used in navigating all major commercial and naval ships, and some aircraft and land vehicles. A gyrocompass is more accurate than a magnetic compass, which relies on the earth’s magnetic field to indicate magnetic north. A gyrocompass points to true north, or geographic north. It is not affected by magnetic forces or by the rolling and pitching of the vehicle.
An instrument called a gyroscope enables a gyrocompass to indicate direction. A gyroscope consists of a rotor (wheel) that is mounted on movable frames. When the rotor spins at high speed, the axle on which it turns continues to point to the same direction, regardless of how the frames are moved. The axle is called the spin axis. In a gyrocompass, the spin axis is automatically positioned parallel to the earth’s axis. The rotor is powered by an electric motor and enclosed in a case that hangs like a pendulum. The information about the direction appears on an indicator on the gyrocompass.
A gyroscope turns over slowly as the earth rotates. This turning, called precession, can cause the spin axis to change direction. To offset errors caused by precession, a gyrocompass has an intricate system of weights and balances. Changes in the latitude or speed of a vehicle also can affect the spin axis, and so the gyrocompass must be adjusted as such changes occur.
A gyrocompass must be protected from vibrations and jolts. Some units float in a container filled with oil to cushion them. On most ships, the gyrocompass is mounted in a compartment below deck. Compass information is transmitted from the gyrocompass to the bridge and equipment. For example, the information may be transmitted to devices that aim guns and guide missiles on warships.
The gyrocompass was invented in 1908 by Hermann Anschütz-Kämpfe, a German engineer. Elmer A. Sperry, an American inventor, also developed a gyrocompass, which was demonstrated successfully in 1911 on the United States battleship Delaware.
See also Gyroscope ; Sperry, Elmer A .
