I'll also mention something I learned watching Jive Turkey on the youtubes. In some way / shape / form this game models the "Deep sound channel" which usually occurs somewhere around 1000-3000 ft. In many cases if you're struggling to pick up a contact, regardless of the layer, go deep and with luck you might be able to sniff him out. Now I don't think this works nearly as well for localizing / TMA purposes but with luck you can at least get a classification out of it and a very general bearing which will at least put you in the right direction.
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