Salute !!!
There are several ways to determine the targets course. The method I use when surfaced is to keep the target at extreme range so he doesn't see you and have the Watch Officer report the bearing and range. Start the stopwatch and plot the position data using the protractor and ruler.
Wait 3 minutes and 15 seconds and do it again. Now you have a plot of his course and by measuring the distance between the two marks you have his speed. It is always a good idea to do this several times at 3 minute 15 second intervals to help reduce any errors. Now you can set up a intercept and GETTUM!
Of course, you must be careful not to get spotted or he will begin to zig-zag and mess up your speed/course data. Or if armed he may take some pot-shots at you !!!!
For submerged workup of a target, review this thread:
http://www.subsim.com/radioroom/showthread.php?t=183225
Watch this video for a great treatment of submerged tracking and attack:
http://blip.tv/nefelodamon
Good Hunting !!!
AD