heading - the direction in which the longitudinal axis of a craft is pointed, usually expressed in degrees from north (true, magnetic, or compass). Also, the instantaneous direction of a vessel’s bow. It is expressed as the angular direction relative to north, usually 000° at north, clockwise through 359°. Heading should not be confused with course. Heading is a constantly changing value as a vessel yaws back and forth across the course due to the effects of sea, wind, and steering error. Heading is expressed in degrees of either true, magnetic, or compass direction.