# How to find cannon elevation angle to fire a projectile to known range?

Hello!

I have a 3d battleship simulation game, with great ship guns. I made a rigidbody projectile, and I can fire it from the gun. I use gravity and a little drag (0.01) on the projectile, to simulate air resistance. The trajectory is computed correctly by the physique engine. For example the gun can fire a projectile up to ~30.000 meters, with 760m/s muzzle velocity at 30 degree cannon angle, exactly like a real 14inch ship gun.

In reality the battleship fire control system is calcule all the firing parameters, the gunners must find only the target range by an optical “range-finder”. The most important parameter is the cannon elevation angle.
So to control the shoots, the firing system must calcule the exact cannon elevation angle for any arbitary firing range. Since the trajectory path with real drag is a very complicated mathematical function, I would like to find an easier way.

So any idea what is the easiest method to find the exact cannon angle for a specifique range? Should I make a simulation scene apart, for call the predict firing datas?