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

To calculate a back azimuth from an original azimuth that is greater than 180 degrees, you need to subtract 180 degrees from the original azimuth. This calculation effectively finds the angle that is directly opposite the original direction on a compass.

For example, if you have an azimuth of 210 degrees, you would subtract 180 degrees to get a back azimuth of 30 degrees. This process is crucial in navigation and map reading, as it allows you to determine the reverse direction of travel efficiently.

In contrast, adding 180 degrees would result in an incorrect value, as it would simply increase the angle rather than finding its opposite. Multiplying by 2 or leaving it unchanged would not yield a valid back azimuth either, as these methods do not provide a logical way to derive the reverse direction. Understanding how to calculate a back azimuth accurately is essential for effective navigation in various military operations.