This app is designed to allow you to calculate a range to a target using a compass. All you have to do is select two fixed points. Go to the first fixed point and take a bearing to the target. Then go to the second fixed point and take a second bearing to the target. Then measure the distance between those two fixed points. The calculated range is the distance from between the two fixed points to the target.
If you found this app to be useful, how about donating a few dollars to say thank you?