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Ok
I have a question about what I'm actually seeing in the water column, the black portions of my SI.
If I'm in 25ft of water, i know I'm seeing 25 ft of water straight down, but is it also showing 25ft to the side of the boat?
In other words, using SI in 25ft of water would i be able to see fish 25ft to the side of the boat in the black areas on my screen ?
Hope this makes sense. Never heard it discussed.
Thanks
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So I’m no pro but let me try at this with what I know. So if u set the range at 100 feet on both sides and your in 25 foot of water, your only scanning 75 foot out the sides. The 25 foot down is part of the range. The black column on the SI screen is below the boat/straight down. Hope this helps and I think this is what your asking. Again I’m no pro on this!Quote:
Originally Posted by brettw
Thanks
Reason I'm asking is i was scanning for crappie under docks. 1st time I ever really did that.
Didn't see much , poles shadows.
A friend told me to get close to the docks and i could see fish in the water column under the docks.
I couldn't pick them out of the orange humminbird background but a black background would be easy.
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Here's a 'bird screen shot of a huge school of crappie under a floating dock. Below is a dock with no fish.
Attachment 375906
Sonar only shows range to object. Depth is straight down, or one side of a right triangle, and range shown on screen is the hypotenuse of the right triangle *. It is not linear. If your depth is 10 feet, and fish is at 30 foot range mark, the distance out from side of boat (assuming fish on bottom) is 28.3 feet per Pythagoras theorem: z**2 = x**2 + y**2. X is depth, and z is range shown on screen. Solve for y. :ThumbsUp
*: assumes flat bottom. if bottom isn't flat, it gets way more complicated. Google "sonar slant range". HTH
No, I don't keep a calculator in the boat. I do have an app on my phone. I just make a SWAG and cast!
:cheers2
You can learn a good bit when bream are bedded. This year I started throwing out markers when it first comes on screen and when it goes off. Then circling around it several times shows me how the screen Vs real world relates to one another.
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The dark water column represents everything within a semi circle equal to (or less than) the water depth ...
Attachment 375940
The bottom detail (left and right) in the SI image is actually touching under the boat. The SI software engineers simply “scooted” these 2 sections outward in the SI image to make room on the display for the water column ...
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Targets in the water column that are the same distance from the xducer will be painted in the SI image as the same distance from the SI image centerline (regardless of where those targets are in the water column).
Attachment 375941
Then use the target shadow to help the “mind’s eye” visualize how high that target is off the bottom ...
Rickie
Rickie,
Thanks for the information. Very help.
And difference in the semi circle between 455. 800, or mega frequencies?
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455kHz and MEGA cover 180°
Attachment 376133
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800kHz covers 130°
Attachment 376134
Rickie
Incredible info! Thank you.
but I dont understand the double image left and right of center line of the crappy school, if the school was under a dock on right why the ghost on the left ?
Ok Rickie
What do you prefer 455 or 800? Looks to me like 800 would show more detail but 455 would show more stuff.
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The answer to your query is in Sonar Quiz #37 here:Quote:
Originally Posted by shaved ice
https://www.crappie.com/crappie/side...nar-quiz-37-a/
Rickie
*I prefer 800kHz when looking at stuff under the boat ...Quote:
Originally Posted by tcounty
* I prefer 455kHz when looking at stuff away from the boat and I can’t get the screen bright enough (SI Sensitivity) with 800kHz to see that stuff away from the boat ...
Rickie