With so many variables ( some dynamic like the wind ) you might be better at starting with a rough guess, and having 4 buttons - " up a bit " ,"down a bit " , " left a bit" and " right a bit " , just like real mortars have been aimed for years 
With so many variables ( some dynamic like the wind ) you might be better at starting with a rough guess, and having 4 buttons - " up a bit " ,"down a bit " , " left a bit" and " right a bit " , just like real mortars have been aimed for years