I just do a radar sweep, mark target position on the nav map, wait awhile and repeat. Draw a line between the two (or three or four) marks and use the compass tool to determine their heading. Using the TM mod though, I've found that most of my targets usually end up with a zig zag course. I hate lining up the perfect solution and approach only to have them zig right before launching my fish!
Happy Hunting,
Howler
