In Arma 3 I am taught to use a compass that marks directions in a three digit number. Yet due to the environment, it is only good for the x axis.
I think that if you could make a direction system off of two three digit numbers. (0-360), we could establish a x and y axis. Thus allowing us to give direction when in flight.
The Z axis is distance, and could be handled separately. (Z axis being depth).
I did come up with this in spurt of the moment. Let me know what you guys think.