Gyro Compass

A gyrocompass finds true north from the precession of a fast-spinning rotor constrained by gravity and the Earth’s rotation, so it points to the geographic pole and is unaffected by the ship’s magnetism, unlike the magnetic compass. It needs electrical power and a settling time of several hours from start, and carries small speed and latitude errors corrected by the unit. Heading from the gyro feeds the autopilot, radar, ECDIS, and gyro repeaters around the ship; SOLAS V/19 requires it on ships of 500 GT and over.