These shots were taken over a large mud flat to show how just a slight adjustment of the motor can effect SI on the motor side.




Up to the yellow line you can see the mud flat left and right. (A)To the left or motor side you can then see the interference from adjusting the motor down a bit and once stopped I then have dead space where the motor is blocking some of the SI signal. (B) You can also see where a interference line shows up to the left. The signal is hitting the motor.





Once the motor is angled back up the interference line goes away and the bottom returns.


Dark areas in the SI view can be made from other things as well. A sloping bottom, shadows from large humps or the other side of a point could give this darker image. A muddy bottom with low Sen. setting could be dark but raising the Sen. will start to bring detail out.

If you notice that this happening on the motor side try to raise the motor some and see if this helps clear up the image.