rnvinc is correct ... and here's a picture describing exactly what he said :

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Taken over a brushpile, and you can see by the 000mph that I was basically "sitting still" (though I wasn't actually tied up/anchored).

Sounds like, to me, that you want to see a down image picture quality rendering of what the cover looks like ... and in constant real time. Not going to happen with SI, DI, or 2d sonar. There must be "movement" for the image to change ... either the boat, or a moving transducer sweeping the area (like the 360 or Spotlightscan).

... cp