1197 di

Even tho I'm not a fan of the 1197 DI (because of the lack of dedicated DI crystals in the Xducer).....

Here's a shot I took Thursday which does emphasize that DI can still be a very good tool in the HB units that use the SI crystals to render their DI images.....

Notice the fish hugging the bottom between the last 2 concrete legs on the right....

Notice the fish to the left of the entire structure (which happens to be the downstream side of the structure exactly where one would expect fish to be staying in the slack water behind the structure)....

Rickie

Is it true, the deeper the water, the better the DI picture?

kool picture

Good Pic man!

Davy Jone's Locker.Thumbs UpThumbs Up

must be the Crappie Motel

The structure is a concrete bridge piling...it sits in 22ft of water and actually extends over 50 ft above the surface of the water.....to the roadway above crossing the lake...

The pic of the structure is actually a little deceiving (for lack of a better term)....

Looking at the image would make one tend to think that the structure only rose 14 ft off the bottom.....this is not the case at all as I'll try to explain....

Once again the user has to understand the shape of the sonar beam used in capturing a DI image in the 1100 series units....

First let's understand how the DI image is formed in the SI unit of this series....

The 1100, 900, 800, and 700 series SI units do not have dedicated crystals in the Xducer to perform the task of creating a DI image on the screen...the DI image is actually derived from the information received using the SI crystals in the Xducer.....the processor just renders the SI information into an DI "looking" image to show in a DI perspective....

In addition, the shape of the SI sonar beam is very wide left to right but very narrow front to back....try to image a "Chinese folding fan" opened up, facing downward and perpendicular to the Xducer..

These 2 points above have been discussed several times...but what hasn't been discussed very much is in how this "Chinese folding fan" shaped beam is shaped in relation to the 455kHZ frequency vs the 800 kHZ frequency....

Take a look at the depiction at the bottom of this post....

Notice the shape of the 455 kHz frequency extends nealy to the surface of the water on each side of the boat (giving total 180 coverage)...whereas the 800 kHz frequency only extends approximately 55 degrees up from the vertical plane on each side (giving only 130 degrees coverage)...

It is this conclusion in the shape of the 800 kHZ frequency that gives the DI image in my OP the optical illusion that the structure only rises 14 ft off the bottom.....because the 800 kHz frequency only has a coverage area of 130 degrees left to right the "upper portion" of the bridge piling is not showing on the image...(I assure you it is a very tall piling)....

Clear as mud right...??

I could have very easily captured the image using the 455 kHz frequency setting and the piling would have shown on the image all the way to the surface of the image...but...because the 800 kHz frequency gives much more clearer images...I was more interested in seeing and determining how the bottom of the piling was actually shaped as I knew from fishing the piling that there was some kind of obstruction around the bottom of the piling...and the 800 kHz frequency would give me a better understanding of what I was seeing on the 1197 screen....

Rickie

Quote:

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Originally Posted by chaunc

Is it true, the deeper the water, the better the DI picture?

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Not sure myself chaunc....

Because I use the DI very little...I just learning myself....

I did learn from this experiment that DI seems to be a better tool around bridge pilings than the 2d or the SI...

Rickie

So the DI on the 1197 is clearer on 800. Gonna have to give that a try next time out. I haven't been very happy with the images i've been getting. They never seemed to be as clear as i thought they should be. Had a couple pics to post but cant find them right now.

Quote:

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Originally Posted by chaunc

So the DI on the 1197 is clearer on 800. Gonna have to give that a try next time out. I haven't been very happy with the images i've been getting. They never seemed to be as clear as i thought they should be. Had a couple pics to post but cant find them right now.

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I have found the 800kHz to be definately clearer than the 455kHz....

Myself, I would only use the 455 in very deep water or very shallow water...

My home lake being KY and Barkley (with maximum depth of 70ft but most in <30 ft) the 800kHz works well...

Because of the shape of the 800kHz only being 130 degrees left to right I would use the 455kHz in shallow water of less than 3ft...

Try this test....

Take a snapshot of any bottom structure that looks interesting...

Scroll thru the views until you get to the "Snapshot/ Recording" view....open the snapshot you just took....

Then change the sonar beam frequency from 455kHz to 800kHz and back...notice the difference in the clarity of the 2 frequencies...

As a matter of fact...while you are studying the snapshot...

Change all kinda of different settings to see how the individual settings change the image....

The actual image that the unit has captured is in very "raw" sonar data format....the user controlled settings in the unit are basically different kinds of filters and such that will change that "raw" data to be the most pleasing to your eye in that certain water condition/depth/clarity...

This is why I don't play well with "Auto"....I will change the settings to please my eye..not what the unit "thinks" I want to see.....

You can also change settings while viewing a recording back on the unit for the very same reasons...the data is in there...change the settings to be the most pleasing to your eye......

I feel that I have learned more by playing with the settings in played-back "Snapshots" and "Recordings" than any live sonar viewing i have done....

Take lots of snapshots and recordings and play with them at home when you are not distracted by fishing....

Make a DC to AC converter so you can take your unit in the house and use the very valuable tool that HB has provided in these units...the "Snaphots and Recordings" feature...

Rickie