DOWN IMAGING -- DOWN SCAN -- CLEARVU: Learn how to use the sonar to become a better bass angler.

Down imaging technology is amazing and it can help us locate more bass and fish. Down imaging can also be called down scan, downvu, clearvu, or many other names depending on who makes the sonar. Humminbird, Garmin, Raymarine, and Lowrance all have different names, but the technology is the same.
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Down imaging technology uses high frequency sonar radio waves which enables the sonar and software to present crystal clear images on our depth finders. It is so good that it looks like a picture is taken underwater. Unlike with traditional 2D sonar, with down imaging, we can make out the differences between fish, rocks, weeds, and tree limbs. You can even distinguish between species of fish and whether or not a fish is sitting above a brush pile.
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Just like all other sonar technologies, down imaging emits radio waves at a specified angle from the transducer. However, the shape of these waves look more or less like a triangle. Down imaging is just presenting you a very small slice of the water column and is paper thin. This is unlike traditional sonar that creates a cone of coverage when it pings its signal. Therefore, when you see an object on your down imaging screen, that object is directly below the transducer, or directly to the left or right of the boat.
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The distance an object can be from the transducer is a function of depth and the angle at which the down imaging sonar signal is emitted. The formula to calculate this is 2 x Depth x tan(angle / 2). If you are sitting in 30 feet of water and you are using the GT54 UHD Garmin transducer (60 degree beam angle with CLEARVU) an object on the bottom can be up to 15 feet either side of the transducer.
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When you use traditional sonar and down imaging together you can gain a wealth of information become a lot more precise with your casting. If you seen an object on down imaging but not on traditional sonar, then you know that that object is just to the left or right of the transducer and outside the cone of coverage from traditional sonar. This enables you to place your casts in better positions or to regraph the area until that school of fish is on both your traditional sonar and down imaging. When you see that picture, that means you are right on top of the fish and you can back off and begin making your casts.