Heading Sensor

A device that supplies a ship’s true heading, the direction the bow points, to radar, ARPA, ECDIS, AIS, and autopilot. The reference may be a gyrocompass meeting IMO Resolution A.424(XI), a transmitting magnetic compass, or a satellite (GNSS) compass using two or more antennas to derive heading from carrier-phase differences. THDs (Transmitting Heading Devices) follow IMO Resolution MSC.116(73). Heading differs from course over ground; AIS transmits both, and a wrong heading input corrupts ARPA target tracking and chart overlay orientation.