How do you calculate a back azimuth if the azimuth is greater than 180 degrees?

To calculate a back azimuth from an angle that is greater than 180 degrees, the correct approach is to subtract 180 degrees from the given azimuth. This adjustment allows you to find the opposite direction on a compass or map. For example, if the azimuth is 200 degrees, subtracting 180 degrees yields a back azimuth of 20 degrees, indicating the direction directly opposite.

A back azimuth essentially provides a way to understand where you came from, allowing you to navigate effectively using the opposite bearing. This method is widely used in navigation and land navigation as it ensures accurate direction for returning or reversing course.

If the azimuth were less than 180 degrees, the calculation would involve adding 180 degrees instead; this distinction highlights why subtracting is the appropriate method for angles exceeding 180 degrees.