SI interpretation...in 3d - (tutorial)

SI interpretation is sometimes difficult for new users...this is basically because the visual perspective of the SI image is different from any sonar display we've ever seen before...

The difficulty in SI display interpretation lies in the fact that the SI display image is a 2 dimensional aspect image of a 3 dimensional underwater world...

Sonar displays are incapable of rendering a true 3 dimensional image.... (well I guess just about any display in incapable of rendering a "true" 3 dimensional image)...

So,.... the SI techno-developers decided to "bend the rules of 2 dimensional displays" and take 1 of the 3 dimensions of the physical underwater world and display it in the same "visual" plane in the SI image as the other 2 dimensions in the sonar display....

There are "3" dimension planes in the actual physical underwater world:
- 1. "Horizontal width"- (rendered into the SI image by the SI Range width that shows as "left and right" on the SI image)...
- 2. "Horizontal length"- (rendered into the SI image by the sonar history that shows as "top to bottom" of the SI image)...
- 3. "Vertical depth"- (rendered into the SI image by taking the actual vertical plane of the "water column" and laying it flat down in the same 2 dimensional plane on the sonar display as the 2 horizontal planes mentioned above...

What I have tried to do with this 3d rendering program is show how the SI unit processor takes the actual vertical "water column" in the underwater world .... and morphs that actual vertical plane data into a 2 dimensional sonar display...

It is my goal to shorten the "learning curve" of SI interpretation for new users that are having difficulty understanding the "3 dimensional underwater world" as seen on the "2 dimensional sonar display's SI image"...

As you watch this video... Keep your eyes trained on the sunken barge in the right SI beam as the "water column" morphs from the 2 dimensional sonar display image to the actual vertical plane of "water depth" in a 3 dimensional visual aspect ....and then the morphs back into the 2 dimensional SI image...

http://www.youtube.com/watch?v=gsS-Lgg4HD0&feature=plcp

Rickie

nice work, helps me some.

Thanks for the video. This type of information will be very useful to present and future SI users.

So, here's my question. When you see something in the "water" (black background), what position is it showing? If it's closer to the center line, does that mean that you are essentially over top or right next to the baitfish/fish, or is it the opposite?

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Originally Posted by filletfetish

So, here's my question. When you see something in the "water" (black background), what position is it showing? If it's closer to the center line, does that mean that you are essentially over top or right next to the baitfish/fish, or is it the opposite?

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Below is a depiction of how objects (fish) are interpreted in the black water column....
http://i477.photobucket.com/albums/r...SIdistance.jpg

The closer the suspended fish is to the SI center line, the closer (left or right) that fish was from the boat's travel path...

The shadow from the fish indicates how high in the water column the suspended fish is...

The farther the shadow is out to the side of the fish - the higher that fish was in the water column...
Rickie

great job Rickie

Fantastic thread

One qustion Rickie, if fish was to side about 15 feet and only 5 feet deep in water that was 20 feet deep,wouldn't it show up in water column,(black space) and at 15 feet and if no shadow would think its right under you?

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Originally Posted by genec

One qustion Rickie, if fish was to side about 15 feet and only 5 feet deep in water that was 20 feet deep,wouldn't it show up in water column,(black space) and at 15 feet and if no shadow would think its right under you?

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Let's work on the 1st of your 2 questions first...
if fish was to side about 15 feet and only 5 feet deep in water that was 20 feet deep,wouldn't it show up in water column,(black space)

This scenario closely resembles fish #3 in the depiction below...(fish this far out to the side (15ft) and this close to the surface (5ft) would unlikely show in the "dark water column rectangle" ....but more likely show in the "bottom coverage rectangle" as depicted)...

Now let's work on the 2nd of your 2 questions....
at 15 feet and if no shadow would think its right under you

This scenario could have a few possibilities...
1. The fish could be so close to the surface that it's shadow would fall way outside the "SI Range" setting....
2. The fish was so small that it wouldn't block enough sonar to cast a good shadow anyway....
3. (May be others I'm not thinkin of)...

Attachment 95732

Rickie

Rickie, I don,t understand, I thought that anything that was less than bottom from transducer would have to show in water column even if it is to one side?

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Originally Posted by genec

Rickie, I don,t understand, I thought that anything that was less than bottom from transducer would have to show in water column even if it is to one side?

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I will work on some modifications to the depictions above to try and find a easier way to explain this ...

(if anyone else "---or Greg---" is following along that has a good explaination of the "dark water column", feel free to jump in here)

Rickie

Notice in the depiction that fish #5 is, in fact, in the dark water column of the Si image.... But that same fish (in the other view from behind) is very close to the SI centerline (boat's path)...

Notice fish #2 and fish #3 are not showing in the dark water column of the SI view..but both fish are still relatively close to the SI centerline (boat's path)...

This means that fish have to be very close to the boat's path to show in the dark water column...

http://i477.photobucket.com/albums/r...SIdistance.jpg

Rickie

Good Stuff on the video Rickie. That is the best way to explain it.

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Originally Posted by rnvinc

This means that fish have to be very close to the boat's path to show in the dark water column...

http://i477.photobucket.com/albums/r...SIdistance.jpg

Rickie

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This is what is confusing me. I've seen TONS of baitfish in the dark water column, but the info returned from the 2D sonar will give a different story. This tells me that there's no way that they would be under the boat...obvsiously outside of the 2D cone.

I'm not at all trying to prove you right or wrong, I'm just trying to figure out how to use the dang thing the way I think I should be able to. Generally when I go right over a ball of bait, it will show on my 2D and it will show on both sides of the dark water column.