A fibre optic gyrocompass is a compass and instrument of navigation. It is sometimes part of a ships set of compasses, which also include a conventional gyrocompass and a magnetic compass. The compass comprises a fibre optic gyroscope sensor, which links to a computer and then locates north. This in turn links to a compass readout to provide a heading. It has very high reliability and requires little maintenance during its service life. The entire system usually includes a sensor unit, a control and display unit, and an interface and power supply unit. It is often linked with the ship's other navigational devices including GPS.