Gyrocompass
A Gyrocompass is a navigation instrument that uses a fast-spinning gyroscope, influenced by the rotation of the earth, to settle on true north. Unlike a magnetic compass it points to the geographic pole, not the magnetic pole, and is not deflected by the steel of the ship or by electrical equipment.
The gyrocompass is the primary heading reference on merchant ships, feeding the autopilot, radar, ECDIS and other systems with the ship heading. A magnetic compass is still carried as an independent backup that needs no power.
Almost every automated navigation and steering system needs an accurate heading, and the gyrocompass supplies true north reliably regardless of the ship magnetism — something a magnetic compass cannot do near steel and machinery. It is the heading backbone of the modern bridge.
What is the difference between a gyrocompass and a magnetic compass?
A gyrocompass finds true north using a gyroscope and needs power; a magnetic compass finds magnetic north using the earth field and needs no power. Ships carry both, the gyro as primary and the magnetic as backup.