This may be old news and I expect it is (yeah I know I've been out of touch and need to get out more) but several years ago I was watching of course a fishing show and the host had a hand held little unit that after clearing the snow from the ice he poured water on it and held this device or a part of in the water on the ice and it gave him the depth and would even mark fish. I figured what a time saver, it would sure eliminate alot of the guess work and the time it takes to drill holes. At that time they were around $150:00 which I thought was a little pricy but on the other hand, less wear and tear on the auger not to mention myself. I don't remember what they are called.