Thread: Sonar Quiz #25

That's the way I took it, I just made the reference to ds and ss to point out what can be done with cone shapes. Sorry if I wasn't clear.

This idea of "target masking" seems like it would only come into play if the boat were moving from deep to shallow up a steep slope or ledge...(how steep...?? I do not know) ...

This would cause the front edge of the cone to contact a rather reflective surface (the upsloping bottom) before it contacted any "fish type" targets under this point ...

The sonar processor algorithms looks for a certain "repetitive" echo that it can define as "Bottom" ...

Then ...any echos (in that same ping) that are farther away than the "Defined bottom" are disregarded ...



Rickie

Originally Posted by rnvinc

This idea of "target masking" seems like it would only come into play if the boat were moving from deep to shallow up a steep slope or ledge...(how steep...?? I do not know) ...


Rickie

This just doesn't seem right.....we know the boat (and the transducer) were in motion. Otherwise we would have a horrible pic. So as the cone moves from deep to shallow, the leading edge of the cone will "see" the fish from the tail to the back to the front and begin making an arch (2D). The targets would not be disregarded because they would start to appear as the angular cone picks up the fish above the current "bottom" that the cone is seeing. If there is masking, it would have to occur when the leading edge of the cone reaches a point above the fish. This may cause a cut off arch, but surely not complete masking. Remember, the point defined as the bottom in this illustration was below the fish and then moved into this position. It's my belief that the true masking would happen when the boat is moving parallel to the drop off

Check this link out. Talks about the"dead zone".

Use your fish finder to locate the structure that holds fish.

Originally Posted by vic n

This just doesn't seem right.....we know the boat (and the transducer) were in motion. Otherwise we would have a horrible pic. So as the cone moves from deep to shallow, the leading edge of the cone will "see" the fish from the tail to the back to the front and begin making an arch (2D). The targets would not be disregarded because they would start to appear as the angular cone picks up the fish above the current "bottom" that the cone is seeing. If there is masking, it would have to occur when the leading edge of the cone reaches a point above the fish. This may cause a cut off arch, but surely not complete masking. Remember, the point defined as the bottom in this illustration was below the fish and then moved into this position. It's my belief that the true masking would happen when the boat is moving parallel to the drop off

Yeah ... wouldn't the fish be "seen" by the 2d cone (front edge) BEFORE it started climbing up the ridge, and just be images in the history of the screen scroll ???

... ya'll are just making my point about 2d being somewhat a useless technology, when it's paired with down scan imaging.

... cp

Originally Posted by apersohn17

Check this link out. Talks about the"dead zone".

Use your fish finder to locate the structure that holds fish.

And I feel this sort of reinforces what I said. This author states: "A 2 dimensional display can only show the shallowest reading it is receiving back." and his illustration shows a boat sitting over a dropoff, but not showing the fish that are below the "shallowest reading". But remember this is NOT a static picture. This boat is moving from left to right. The transducer will go from shallow to deep as the boat moves, so the "shallowest reading" will gradually go deeper and deeper, and then start showing those fish on the downslope, altho the fish would probably form even less of an arch than if the boat were moving from deep to shallow as in Rickie's illustration. If the boat in the illustration remains in ONE place, then it will show a flat bottom with no fish.

Originally Posted by CrappiePappy

... ya'll are just making my point about 2d being somewhat a useless technology, when it's paired with down scan imaging.

... cp

I'm not much good at finding or catching fish, cp, but I have started using a split screen with both 2D and DI when I stumble onto a brushpile. The DI gives me that true picture quality, but when I want to ease in close, the 2D tells me when I'm getting there by showing echos coming from the front edge of the cone.

The actual sonar image that Rickie posted with the question demonstrates the issue.....The boat was moving up the slope in that image.