Bearing (navigation)

In navigation bearing may refer, depending on the context, to any of: (A) the direction or course of motion itself; (B) the direction of a distant object relative to the current course (or the "change" in course that would be needed to get to that distant object); or (C), the angle away from North of a distant point as observed at the current point.

Absolute bearing refers to the angle between the magnetic North (magnetic bearing) or true North (true bearing) and an object. For example, an object to the East would have an absolute bearing of 90 degrees. Relative bearing refers to the angle between the craft's forward direction, and the location of another object. For example, an object relative bearing of 0 degrees would be dead ahead; an object relative bearing 180 degrees would be behind. Bearings can be measured in mils or degrees.

The US Army defines the bearing from Point A to Point B as the angle between a ray in the direction of north or south, whose origin is Point A, and Ray AB, the ray whose origin is Point A and which contains Point B. The bearing consists of 2 characters and 1 number: first, the character is either N or S. Next is the angle value. Third, the character representing the direction of the angle away from the reference ray - thus, either E, or W. The angle value will always be less than 90 degrees. For example, if Point B is located exactly southeast of Point A, the bearing from Point A to Point B is S 45° E.

The US Army defines the azimuth between Point A and Point B as the angle, measured in the clockwise direction, between the north reference ray and Ray AB. For example, if the bearing between Point A and Point B is S 45° E, the azimuth between Point A and Point B is 135°. The angle value in a bearing can be specified in the units of degrees, mils, or grad. An azimuth is specified in the same angle units.

A bearing can be taken on another vessel to aid piloting. If the two vessels are traveling toward each other and the relative bearing remains the same over time, there is likelihood of collision and action needs to be taken by one or both vessels to prevent this.

A bearing can be taken to a fixed or moving object in order to target it with gunfire or missiles. This is mainly used by ground troops when using an air-strike on the target.

A bearing can be taken to a person or vessel in distress in order to go to their aid or, when that is not possible, to report the person or vessel to authorities or someone who can go to their aid.

...
Wikipedia