Author Topic: What is wrong with my SI images  (Read 5430 times)

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Offline einsteins

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What is wrong with my SI images
« on: May 29, 2012, 04:59:15 PM »
Hi All

I am certainly a newbie still with this technology.
I took a recording this weekend of a strip mine lake and noticed a lot of something in the water column and the bottom images were not so clear.
I have not seen this matter in the water column in any of my previous sessions. Maybe I messed up a setting on the unit somewhere.

Here is a screenshot:


I did adjust the brightness and contrast in Humviwer to help make the image more defined.

Any imput is greatly welcome!

Thanks
einsteins
« Last Edit: May 29, 2012, 05:00:43 PM by einsteins »


Offline Rüdiger

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Re: What is wrong with my SI images
« Reply #1 on: May 30, 2012, 12:37:52 AM »
Hi Einsteins

Only sonar targets with clear outlines and solid strucktur give a clearer image. With a permanently mounted sensor movements cause the boat to a deterioration of the image, among other things, therefore one uses a towfish.
Use 800 kHz, a high frequency gives better resolution at lower coverage.

mvh
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Offline einsteins

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Re: What is wrong with my SI images
« Reply #2 on: May 30, 2012, 06:04:13 AM »
Thanks
I must have set it to 200 sometime while playing with the unit.
Do you think that will take care of all of the interference in the water column ?

Thanks!

Offline Roddy

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Re: What is wrong with my SI images
« Reply #3 on: May 30, 2012, 07:57:09 AM »
einstins, Try this, Take a glass jar full of water from the pond to the your State Water Quality Office and ask to have it analyzed. I thank what you see in your screen shot is a Algae Bloom. Is that time of the year.
0
Roddy
« Last Edit: May 31, 2012, 09:00:16 PM by Roddy »
Scan,Scan and Rescan Roddy

Offline einsteins

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Re: What is wrong with my SI images
« Reply #4 on: May 30, 2012, 08:15:48 AM »
Thanks Roddy

This water was crystal clear with visibility to around 15ft or so.

When I used the unit before in a different lake with visibility at about 1ft the water column showed what I would consider normal. (with some but not as much water column matter)
Here is a shot from my first recording session in 1 ft visibility water


I am not discounting what you say is true just trying to understand 1) If I am using the unit correctly ie; settings, etc. and  2) How to understand what I am seeing on the screen.

I appreciate your help!!

Eins

Offline sonar2000

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Re: What is wrong with my SI images
« Reply #5 on: May 30, 2012, 09:48:13 AM »
You might try setting the si range to 20 feet over the depth.
Have you recently updated the unit code?

Chuck

Offline einsteins

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Re: What is wrong with my SI images
« Reply #6 on: May 30, 2012, 11:00:08 AM »
Hi Chuck

Thanks for your reply...

I updated the unit to the most recent sofware version in March when I bought it.

einsteins

Offline SonarTRX

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Re: What is wrong with my SI images
« Reply #7 on: May 30, 2012, 01:25:51 PM »
Hi Einsteins,

Does all your recordings show more overall noise in the right-side SI channel than the left side?

It is most visible in the water-column of the R00002 sample, but there also seems to be more "snow" in the water-column on the right side of the R00005 recording...)

Tore

Offline sonar2000

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Re: What is wrong with my SI images
« Reply #8 on: May 30, 2012, 03:55:08 PM »
I dont think that code is the issue as the update was a while back.
Try the following:
1. Decrease your si distance to about 20 to 40 feet over the depth.
2. Decrease your sensitivity.
3. Set your depth to auto

Lets see where this takes you.

Chuck

Offline Bob B

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Re: What is wrong with my SI images
« Reply #9 on: May 30, 2012, 04:23:59 PM »
Just another thought....had you motored over this area before doing this scan.  Almost looks like a lot of prop wash.
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Offline einsteins

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Re: What is wrong with my SI images
« Reply #10 on: May 30, 2012, 07:21:59 PM »
Hi all

I really appreciate all of your input...
Here is some more info
Transducer is mounted on my Terrova TM
The very top image from this last saturday was taken from using the TM.
The second image in this post was taken from having the TM in the water and idling the engine at about 2 MPH.

On the first image I tried to keep the range to 2 to 3x the depth as I read that is a good rule to follow.
This was the first time I had used it in any depth greater than 20ft. (my home lake is 18ft deepest)

I dont remember seeing all of the clutter in the water column on my screen as I was recording the run this last Saturday.

Not sure if any of this helps but thought it might be good to add this info.

einsteins

Offline Bob B

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Re: What is wrong with my SI images
« Reply #11 on: May 30, 2012, 07:35:09 PM »
Referring to the first image, I think the sensitivity setting is too high....this will cause you to have more surface clutter.  (The second return on the 2D view indicates this.)
Were you close to a hard bank on the left side?  The right side is much weaker for some reason.

It is harder to get a "pretty" SI from the trolling motor.  This doesn't look like trolling motor interference, however.


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Offline xSilmarilSx

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Re: What is wrong with my SI images
« Reply #12 on: May 30, 2012, 11:55:42 PM »
Something people should be aware.. Is that in Humminbird units, when you do a full record of the sonar signal, your record the RAW data. So a change in sensitivity or anything else will not show on the HumViewer software.

You could whack the unit setting way off, and still have a good view (or bad view) in HumViewer.

Offline sonar2000

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Re: What is wrong with my SI images
« Reply #13 on: May 31, 2012, 07:33:00 AM »
Xsil.  good point about the viewer program. Thanks for the reminder.

Chuck

Offline einsteins

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Re: What is wrong with my SI images
« Reply #14 on: May 31, 2012, 08:56:21 PM »
Referring to the first image, I think the sensitivity setting is too high....this will cause you to have more surface clutter.  (The second return on the 2D view indicates this.)
Were you close to a hard bank on the left side?  The right side is much weaker for some reason.

It is harder to get a "pretty" SI from the trolling motor.  This doesn't look like trolling motor interference, however.

I was close to the bank on the left side in that particular place.
I am thinking of getting a second 798ciSI for the counsel and putting that transducer on the back of the boat. I would use this as my main recording unit.

Problem is they are getting hard to find...I dont want to get an HD as the cost is considerably more and for me I dont gain much.

Someone mentioned I was on the wrong frequency also....it that correct?

Thanks
eins

Offline Bob B

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Re: What is wrong with my SI images
« Reply #15 on: June 01, 2012, 05:55:38 PM »
While it is true that 800khz can give better image clarity, it is not an option on the 798.

Another tip that I would offer is to consider just scanning to the side away from the bank when scanning a bank.  You will see a lot more stuff if you drive as close to the bank as possible and scan out.....especially on a steep bank.  The slope of the bank often "hides" a weak return such as what you might get from brush if you are scanning into the bank.  If you scan out, you can see it better against the water column.
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