Author Topic: depth does not match each other  (Read 8537 times)

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Offline bjrose

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depth does not match each other
« on: June 22, 2012, 03:38:07 PM »
i hpoe this screen shot to explain what i mean loads ok. if it does notice the top depth reading shows237 feet.
then the colored chart shows about 135 feet. any ideas?


Offline sonar2000

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Re: depth does not match each other
« Reply #1 on: June 22, 2012, 03:51:44 PM »
dont know.   I would not think the unit will read thru 100 feet of soft bottom but kind of looks like that...
Chuck

Offline Humminbird_Greg

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Re: depth does not match each other
« Reply #2 on: June 22, 2012, 04:15:10 PM »
Is this over some type of underwater structure, school of fish, edge of a drop off or something like that?
What is your Si sonar showing in this area?
Does it change if you stay stationary over it?

It’s something fairly hard or dense as it is reflecting a good bit of sonar from that water depth.
Greg Walters at Humminbird
gwalters@johnsonoutdoors.com

Offline sonar2000

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Re: depth does not match each other
« Reply #3 on: June 22, 2012, 04:20:12 PM »
Look at the graph on the very right of the screen .  It seems a bit soft to me...
dont see much in the water column of which 2d is generally a good display for water column stuff. no fish. vegetation or out croppings. Looks pretty clear underneath the boat.
I would think it is reading thru the bottom to the hard part..
although 100 feet of bottom return is something unusual..

Maybe he can shed some more light on this..

Chuck

Offline Humminbird_Greg

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Re: depth does not match each other
« Reply #4 on: June 22, 2012, 04:33:58 PM »
Think about it Chuck; at 237 feet of water the 20 degree 200kHz beam would be about 83 feet wide.  If he were passing by some trees (or some other tall structure), the leading outside edge of the sonar beam would start picking up weaker sonar returns first before you would see the stronger sonar returns when the boat was more directly over the trees and they were more centered, followed by weaker sonar returns again as the trailing outside edge of the sonar beam was still picking up the trees.

We don’t know his unit settings and certainly do not know what could be under the water he was on.

Interesting screen snapshot though.
Greg Walters at Humminbird
gwalters@johnsonoutdoors.com

Offline sonar2000

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Re: depth does not match each other
« Reply #5 on: June 22, 2012, 05:18:40 PM »
Yep it is interesting.  From old 2d days it does not seem to be much in the water column though. I still think it is reading thru the soft bottom and getting hard return deeper..
I saw this a lot on another older brand of years past 2d...200 khz..but the bottom reading then was from the 1st bottom return..


Chuck

Offline bjrose

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Re: depth does not match each other
« Reply #6 on: June 22, 2012, 10:45:54 PM »
only second time out so maybe settings learning curve. everthing was fine first part of the day then the second part these readings went on constantly no mater depth or type of bottom. the readings were all off. maybe sensitivity set to high or something simple like that. i will try restoring defaults and see.

Offline sonar2000

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Re: depth does not match each other
« Reply #7 on: June 23, 2012, 08:33:43 AM »
Yes by all mean play around with settings.
I am a bit suprised at the depths you are working that you see this issue.

Keep us informed of progress and changes you make and results you see.

Chuck


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