[Soundman]

Originally Posted by joegrundman

it's possible to do, and there are tutorials on how to do it, including one written by me a couple of years ago, but it's not really historical. Purely passive sonar only solutions i think only really came into being in the cold war era, when turn-count technology was much more sophisticated and one was able to identify the exact boat by it's sound signature

A more historical method that does a lot of the work for you, but not all of it, is upon getting a hydrophone contact, up your speed a bit and point your boat directly at the target.

Now observe whether the target is swinging to pass your port or starboard. That is, if the bearing to target goes from 000 to 357, then it will pass to your port on your current heading. If the bearing goes from 000 to 003, it will pass your starboard on your current heading.

If the target will pass your port, turn 80degrees port; if the target will pass your starboard, turn 80 degrees starboard

try to find a speed that means the bearing to target remains constant.

you are now on a collision course with the target, and will eventually find it

I like that, it's very clever. It's very logical and simple to understand, yet most people would not think of using this technique.