Knowing exactly where the divers are running is really only important if your targeting the bottom. Salmon will swim up a long ways to hit, or see a bait. I have watched them on the graph rise 30-50' to check out a rigger bait. The TD device is a good idea, and will confirm what they are running at. Often when we are done fishing for the day, we will troll toward the peer, and watch when the divers hit the bottom. Often I will say to my son " that one will stat hitting soon", and sure enough it dose. The 1/2, is very close for a mag diver (set at 1.5), and 1/3 is very close for a regular diver (set at 2.5)