I’m not totally sure I understand the problem - so please correct me if I’ve misunderstood.
You have (x, y, z) data for the elevation of your volcano (above some reference - e.g. mean sea level).
Do you want your plane to fly in a closed loop around the volcano, at a constant height above the underlying ground? And then, do you want the coordinates of this loop?
If the above is what you want to do, then I can think of a reasonably easy way to do it using GMT tools. But please let me know if that is actually what you’re trying to achieve.