Side-scan or side-imaging has been around for a few years, long enough for units with such capabilities to be more affordable to the average user, providing applications for all kinds of fishing. Side-scan is still sonar; the difference lies in the beam and projection angle.
The revolution started with down-scan technology, which incorporated the ultra-thin, high-frequency beam that allows for the picture-like quality of the images on the screen. If you thought you were looking at a tree on your conventional sonar, now you know you were looking at a tree, but it did little to shed light on the areas not directly under your boat.
With traditional down-facing sonar, an 83 kHz beam will render a cone of coverage of 60 degrees, which basically equates your coverage to your depth, which isn’t very effective in shallow water.
Side-scan combines the ultra-thin, high-frequency beam with a transducer that projects the beam outward. Then, it layers the returns in slices for a 180-degree visual. The biggest challenge is adapting to and interpreting that return. After years of watching a screen scroll from left to right, your side-scan screen will scroll from top to bottom, showing you what you have just passed. Units equipped with GPS will often allow you to mark cover for a later return
Hard targets like wood, rock and rising terrain will be more brightly colored than the areas surrounding it, and they will cast a sonar shadow that can be used to interpret the height of the object. The trained eye can also distinguish bait and fish from returns that look like a small cloud representing a school of baitfish or markings similar to grains of rice that depict larger fish.
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