What is the first component of back azimuth calculation when the measured azimuth is less than 180 degrees?

When calculating the back azimuth of a measured azimuth that is less than 180 degrees, the correct first step is to add 180 degrees. The concept of back azimuth refers to the direction directly opposite the current azimuth. For azimuths less than 180 degrees, this is done simply by adding 180 degrees to the measured azimuth. This calculation ensures that you arrive at the correct opposite direction.

For example, if the measured azimuth is 120 degrees, to find the back azimuth, you would add 180 degrees, which results in 300 degrees. This approach ensures that you remain within the 360-degree compass system, as you effectively shift the angle to the opposite side of the circle.

Adding or subtracting other values, such as 90 degrees or 180 degrees inappropriately, would not yield the correct back azimuth in this scenario, potentially leading to confusion in navigation or orientation.