Double bottom reading?

[Legend LE-195]

When I set my echomap depth range to manual mode and zoom out I'm getting a false bottom reading below the actual bottom, are my settings incorrec or need fine tuning?

[LWINCHESTER2]

Very normal. In fact there are folks who set the manual range out enough just to see the second return and tune their unit for looking at it. It's a science that I'm not up on but I know there are folks who analyze that second return for interpretation. The story is that the ping hits the bottom, then bounces to the surface and is reflected back to the bottom and the unit picks it up on both bounces. The second one, taking longer, shows deeper. There is probably someone who reads this board who could instruct us on the particulars of how to interpret it.

[Wayne P.]

Very normal. In fact there are folks who set the manual range out enough just to see the second return and tune their unit for looking at it. It's a science that I'm not up on but I know there are folks who analyze that second return for interpretation. The story is that the ping hits the bottom, then bounces to the surface and is reflected back to the bottom and the unit picks it up on both bounces. The second one, taking longer, shows deeper. There is probably someone who reads this board who could instruct us on the particulars of how to interpret it.

It is one way to determine bottom hardness and having Sensitivity high enough to detect fish. An old school technique for back in the flasher sonar days.
Also a way to not have Sensitivity so high that the depth readout is affected.

[RangerRic]

Yeah, I remember that - if you got a second echo, you were dialed in ....