The OTC mod has an option for American radar from the beginning of the War. Planes show up on radar, but the radar blip moves accross the screen quickly. When I see a radar blip moving too fast for a ship, I dive or get ready to dive.
My problem with map contacts enabled is that the blips never disappear, as they would do if being tracked via radar. When map contacts are disabled, I use sonar to plot the target's course. How do I do that? (See below.)
For speed, first I measure the time it takes a target's bow to pass 0 degrees on the periscope. Second, translate the measurement into yards per second, and third, calculate speed by multiplying yds. per second x 180 (i.e. multiplying by 3 minutes). Gee, where did I figure speed calculation and map plotting with map contacts disabled out? How about Warner Sobe's sonar only tutorial and Double R's
(you gotta love CapnScurvy!) Sonar Only - By God tutorial? If you look, you might be able to find a thread that explains how to do it. (Rofl.)