方位角と方位

The azimuth of a line is the clockwise angle from the north end of the reference meridian, typically used in plane surveys.

The magnitude of an azimuth can range from zero to 360 degrees.

For example, the forward azimuth of line AB is 55 degrees. To find the back azimuth or the azimuth of line BA, add 180 degrees to get 235 degrees.

The bearing of a line is expressed as a reference direction, an angle of inclination, and the direction in which the inclination is measured.

The reference directions are always the north or south ends of the meridian, and the angle is always 90 degrees or less.

The bearing of line AB is North 55 degrees East, meaning the line is inclined 55 degrees eastward from the north. Similarly, the bearing of line BA is South 55 degrees West, found by reversing the directions of the bearing of AB.

When a line moves through different quadrants, only the angle changes for its azimuth. In contrast, for bearings, both the reference direction and the direction of inclination change along with the angle.