How is a back bearing defined?

A back bearing is defined as the reciprocal of the original bearing. When you take a bearing to a point, the back bearing is the direction you would need to turn to go back to your starting point from that position. In practical terms, if you have a bearing of, say, 120 degrees, the back bearing would be 300 degrees, which is found by adding or subtracting 180 degrees.

This concept is crucial in navigation because it allows sailors and pilots to trace their route back accurately or to understand their position in relation to their starting point. Understanding back bearings helps maintain situational awareness and ensures that navigators can return to their original location if needed.

Other definitions like relative bearings, magnetic north angles, or bearings at 90 degrees are related to the way position and direction are described but do not define back bearings accurately.