The gyrocompass measures the ship’s heading with reference to true north.
The heading is used to calculate true wind speed and directions based on relative measurements from the wind anemometer in the foremast.
The compass gets its input from the speed log (for correction of speed error) and the GPS (for correction of latitude error).
The compass is connected to the autopilot which steers the ship when it is not in manoeuvring conditions.
The autopilot keeps the ship’s course as set by the navigator by taking into account environmental disturbances from waves, wind and currents, as well as the ship’s sailing conditions such as speed, loading conditions and trim.
Rudder commands from the autopilot are partly based on setting applied by the navigator and partly by a mathematical model of the ship programmed in the autopilot.
To achieve the most economical steering for the ship it is essential that settings given to the autopilot are in accordance with weather and load conditions.