I'm a shallow water fisherman. If you have just the map on with depth turned OFF you can use you contour lines to somewhat tell you the depth your in. you have sonar, side imaging that transmit sounds into the water.
1. When you have just the map on, I would not think just the map would transmit sound. correct me if I'm wrong.
2. When having the map on with it reading the depth, I would think that transmit sound pinging the bottom. ?
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