Hi this post is here because I found it difficult using manual TDC in SH2 until now
goto
http://www.communitymanuals.com/shiii click on manual targeting for sh3
it shows you if you don't understand the basic concepts behind TDC mathematics like most of us poor sods how to find the AOB (angle off the bow) using a simple sum/equation. The sum is universal for the SH games. If your asking why would you want to use math in a game well the answer is you kind of have to to operate a manual torpedoe data computer it's not that hard and I find it makes the game more fun anyway.
By the way was this the real method used to calculated the AOB if so how did the submariners determine the heading variable to make this work