In navigation, the heading of a vessel or aircraft is the compass direction in which the craft's bow or nose is pointed. Note that the heading may not necessarily be the direction that the vehicle actually travels, which is known as its ''

course Course may refer to: Directions or navigation * Course (navigation), the path of travel * Course (orienteering), a series of control points visited by orienteers during a competition, marked with red/white flags in the terrain, and corresponding ...

'' or ''track''. Any difference between the heading and course is due to the motion of the underlying medium, the air or water, or other effects like skidding or slipping. The difference is known as the ''drift'', and can be determined by the '' wind triangle''. At least seven ways to measure the heading of a vehicle have been described.

Notation

Heading is typically based on

cardinal direction The four cardinal directions, or cardinal points, are the four main compass directions: north, east, south, and west, commonly denoted by their initials N, E, S, and W respectively. Relative to north, the directions east, south, and west are at ...

s, so 0° (or 360°) indicates a direction toward true north, 90° true east, 180° true

south South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...

, and 270° true west.

TVMDC

TVMDC is a mnemonic for converting true, magnetic and compass headings. TVMDC is a mnemonic initialism for true heading, variation, magnetic heading, deviation, compass heading. The most common use of the TVMDC method is correcting courses during nautical navigation.

Background

The Geographic North Pole around which the Earth rotates is not in exactly the same position as the Magnetic North Pole. From any position on