# Direction angle

**Direction **angle (usually denoted by) is a term used in mathematics and geodesy for the angle between the north direction ( grid north ) and a straight line or line . The directional angle of a line from point to point is given from the parallel to the north-facing x-axis through the point to the right, i.e. clockwise.

In navigation , the direction angle is referred to as the course angle , compass angle or march number. It means the same size.

## calculation

Common spellings for the direction angle are or . The index denotes the starting point or position and the second index the end or destination point.

For the direction angle in a geodetic coordinate system , i.e. H. with geodetically positive or mathematically negative direction of rotation , the following relationship applies:

When calculating polar coordinates from Cartesian coordinates, the quadrant in which the direction angle lies must be taken into account. The function is suitable for this :