Im gonna say they would show. The 2d shows 11ft. but the fish are about 17 ft. when the 2d beam hits the bottom it levels out it doesn't follow the slope.Quote:
Originally Posted by kosmo
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Im gonna say they would show. The 2d shows 11ft. but the fish are about 17 ft. when the 2d beam hits the bottom it levels out it doesn't follow the slope.Quote:
Originally Posted by kosmo
I think it is possible that the fish could have been in the outer fringes of the DI fan beam and be somewhat missed by the 2d cone ...
However...this example would tend to follow the explaination from Airmar ... (the notable aspect being the sharp rise in the bottom) ...
From Airmar ...
http://www.airmartechnology.com/uplo...Operations.pdf
What is target masking?
There are areas within the transducer's range which seem to be invisible to the echosounder. This is know as target masking. It can happen if the lake or sea bottom drops off suddenly or contains a large rock. The sound waves will bounce off all of the sea bottom within the sound beam and return as strong echoes. The echoes from the highest point, the rock or dropoff, return to the transducer first, falsely indicating the apparent depth of the bottom. Small fish below the highest point will produce relatively small echoes which will return after the larger ones. Therefore, fish can be swimming around the sides of a large rock or a dropoff, be in the sound field, and yet remain invisible to the echosounder.
Attachment 274224
Rickie
I wonder if part of the problem is the 2d td installation? Maybe kicked up in the back?
Kos I believe 2d does have blind spots, on the edge of said cone, the bottom of the cone is not flat it is shaped just like an ice cream cone upside down with a round scoop of ice cream in it , so now the cone has spots that don't reach nor read bottom, 2d sonar gives bottom readings from the first contact made with the bottomQuote:
Originally Posted by kosmo
I'm not much good at explaining things, I hope I got this correct
I.m thinking that not only those fish would not show, but even, let's say a diver that was six feet tall standing on the bottom and close to that sharp break, would not show on the 2d, but would be displayed on the di.what do yeall think?Quote:
Originally Posted by wilbur
Kos you are correct, my thinking is that if the diver is at a level below where the 2d cone makes first contact with the bottom he will not show up on 2d but he would on DI
here's a crude picture I did in paint real quick to kind of show my thoughts
I hope I'm correct if not I was told wrong or miss understood by my late uncle that was a sub man in the cold war era
+1 :ThumbsUpQuote:
Originally Posted by kosmo
so if this is the case, when traveling perpendicular to a sharp dropoff and you see fish returns, can you assume the fish is on the leading edge of the cone since the rest is dead zone?Quote:
Originally Posted by short grub
:scratchhead
I don't agree, but I've been wrong many times, just ask my wife. If this was the case why would the sound waves travel in a circular pattern? With the technology now they can direct the beams, just look at down and side scan. Also the rest of the signal continues and bounces off and is returned to the td. Now what the processor does with I don't know. I believe that if a 6' diver was standing at the bottom of the drop he would show up, I've seen to many bucks and beds right at the bottom of drops on 2d and down scan. Surely if you can see a 5 gallon bucket with some sticks at the bottom of a drop you could see a man. No disrespect intended, just my opinion.Quote:
Originally Posted by short grub