Compass

A compass is the fundamental direction-finding instrument of marine navigation, providing the officer of the watch with a continuous indication of the vessel's heading relative to either magnetic north or true north. Bowditch (American Practical Navigator) distinguishes three types in regular shipboard use: the magnetic compass, the gyrocompass, and the gyro-stabilised fluxgate compass. Under SOLAS Chapter V, Regulation 19, most ships are required to carry both a gyrocompass or equivalent and a standard magnetic compass as a backup, ensuring redundancy if either fails. In practice, the OOW uses compass readings constantly: to steer a course, to take bearings of terrestrial or radar targets, and to verify the vessel's heading during course alterations. The gyrocompass output feeds the autopilot, ECDIS, and AIS transponder, making its accuracy critical across multiple systems. Any error in compass reading—whether from gyro drift, variation, or deviation—must be detected, recorded, and corrected before it propagates through the navigation system.