How
A back azimuth is very easy to calculate in degrees. First, shoot your azimuth. Then, calculate according to the following rules:
IF YOUR AZIMUTH IS
Less than 180 degrees, then add 180 degrees to get your back azimuth
Greater than 180 degrees, then subtract 180 degrees to get your back azimuth
Exactly 180 degrees, or South, then your back azimuth is either 0 or 360 degrees, both of which are, of course, North
Here is a little practice exercise for you:
Azimuth |
Back Azimuth |
135 |
|
292 |
|
Why do you need it
The most common need for a back azimuth, in my experience, is reversing a path. If you have shot an azimuth on a landmark and approached that landmark only to find out that your path will not work, you may need to reverse that path all the way back to your last known point. You will use the back azimuth to find the exact direction you need to follow to reverse your path. Pace counting will be very useful here as well because it will allow you to easily return to an exact point.
Another possibility is that you have a very good landmark behind you, and would like to shoot an azimuth on that landmark, and then travel in the exact opposite direction.
Here are the answers to the exercise above
Azimuth |
Back Azimuth |
135 |
135 + 180 = 315 |
292 |
292 – 180 = 112 |
Tags: Azimuth, Back azimuth, navigation
can you draw the compass i think with numbers which shows the true azimuth?