When side imaging a drop off always position your boat to shoot down the drop on the first pass if possible. This approach will highlight any wood sticking out from the drop. Wood returns a very weak sonar signal, but when silhouetted against the water column which delivers little return, wood stands out.
The following is a tree side scanned from the top of the drop looking out into deeper water.
Here is the same tree scanned with the boat on the deep side of the drop looking back at the face of the drop. Hard bottom returns a strong signal and virtually obscures the tree. In a scenario like this really pay attention to small shadows. If you feel like the area could hold fish go back and investigate the shadows with downscan.
Navico (Lowrance) provides the following guidelines on the limitations of side and down scan coverage:
In 20′ of water using 800 kHz the maximum capability of the HDS system is 35′ per side. Couple that with 20′ downscan coverage and you can view a 90′ window. No reason to set the side range any higher because the system is not capable with those settings. 455 kHz will increase distance at the expense of resolution per the chart. Humminbird specs are very similar.
Compared to conventional sonar, 90′ is pretty good though. A 200 kHz (20 deg cone) freshwater transducer would show 1/3 of the bottom depth or roughly 7′. The 83 kHz would display double that or 14′. 90′ of coverage vs. 7’…this is why bigger screens are important for side scan imaging.
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