If you are using a jigging rod, pinch the split shot on at the waterline and however far the split shot is above the waterline is the distance the lure or bait is off bottom. Of course, there is no need for this if you are using a jig or a sinker with a bait that is heavy enough to feel the bottom.

UNDERSTANDING SONAR
Sonar is particularly effective when fishing deeper water because the signal cone increases in diameter with increasing depth (with increasing distance from the transducer).

Understanding how sonar signals function is essential to fishing the entire water column, not just close to the bottom, but also everywhere between the bottom and the ice. Without sonar, fishing the middle depths in deep water is next to impossible, or at least so time-consuming that it is not practical.

Sonar functions by sending a signal from the transducer. That signal bounces back to the transducer from the bottom and from anything it strikes between the bottom and the transducer. What you see on the sonar screen is an interpretation of those signals, which bounce back to the transducer.

The signals that emanate from the transducer travel in the form of an ever-widening cone. Within the first few feet beneath the transducer, you are seeing what is immediately beneath the transducer. Using a cone with an angle of 10 degrees, that cone has a diameter of a little more than 5 feet at a depth of 30 feet. A 50-degree cone has a diameter of about 28 feet at the same depth.

At a depth of 60 feet, the 10-degree cone has a diameter of 11 feet, while the 50-degree cone has a diameter of about 56 feet. (Now don’t go checking my math. I’m an outdoor writer, not a mathematician!)

Some fishermen prefer to use cones with a wider diameter because they can see more. However, the problem with this is that the wide view can be confusing. You are seeing much more than what is directly beneath the hole through the ice. This also distorts the apparent depth of fish. Fish that are along the outer edges of the signal cone appear to be deeper than they actually are. A fish at the outer edge of a 50-degree cone at an actual depth of 60 feet appears on the sonar screen to be down more than 65 feet. And rather than being under the hole they would actually be about 28 feet off to the side, far out of reach or sight of any lure or bait.

Despite all this, it does help to know what is going on down there.

Perhaps the single most important piece of information you can get from your sonar screen is verification of the presence of aquatic life, not necessarily the specific game fish you hope to catch. Just knowing that something is down there, ideally baitfish that will attract game fish, lets you know that you are in the right vicinity. For this a wide-angle cone is a clear advantage. Get your lure or bait into the same zone where you have detected bait and you will have improved your odds for success tremendously.