LiveScope Questions for Deep Thinkers - LS vs SideScan

PawPaw Gene and myself are good friends. A day or so ago he brought up a question that really made me wonder.

Why does SideScan show shadows (behind objects) and LS does not?

The technologies are different and Gene and I are curious to learn.
Can anyone help us out?

By-the-way
Gene is still dealing with Myasthenia Gravis (MG). It’s a heck of a disease, but he is a trooper. We talk on a regular basis and he is fighting the battle. He was diagnosed about a year and a half ago after only a couple of trips with his brand new Livescope. We are still planning to fish together and I plan to show him the things I’ve learned since he was forced off the water. Please continue to pray for our buddy…

Good question, Dan !!

Livescope in Perspective Mode shows shadows, so it may just be the shadows are there when using forward facing mode, but the bottom glare swallows up those shadows or the shadows disappear in the distance. :dono

Then again it could be the design of the software to show the on-screen images differently. Sidescan takes images as the boat moves, while Livescope takes images continuously, whether or not the boat is moving. If the boat isn't moving or is moving very slowly, Sidescan images are almost static or collectively placed on top of each other and basically smeared across the screen. Livescope simply continues to show a "live" screen presentation, capturing movement & static images even while the boat isn't moving.

It's kinda like : Sidescan = camera pics taken in rapid succession & Livescope = video camera images.

My 360 also shows shadows. I think that the shadow vs no shadow in views is in the programming of what story or image that the marketing gurus specified to the programmers.

SideScan, 360, and landscape/perspective are generated into an image as if the user were ”hovering above the lake bottom looking down thru the water” ...

2d, DownScan, and FFS are generated into an image as if the user were ”standing on the lake bottom looking sideways thru the water” ...

Rickie

I am waiting for a reply from Garmin. Will post their reply when it arrives.

I’ve asked Garmin techs many times why they didn’t have a forum for questions like this. They supposed it was because Garmin didn’t want to expose their proprietary technology. Not sure how true that is, but the questions about Garmin forums still remains.

As far as I am aware, user to user is our only source for unanswered questions. And in many cases we are just quessing.

I rec’d a prompt reply from Garmin. Below are copies of our conversation. To be honest. Have yet to learn much from the replies. Maybe someone reading these replies can explain and clarify.

Me -
Why does SideScan show shadows and LS FFS doesn’t?


Why does LS perspective show shadows and LS FFS doesn’t?


Garmin -
Side-scan sonar from a GT56 differs from LiveScope in that the GT56 only uses one element for each side, thus when the signal hits a target, the area behind that target does not give a return. Think of it like shining a flashlight at a wall. If you only use one flashlight and move your hand into the beam, there will be a shadow cast on the wall, but if you add a second flashlight at an angle the avoids the hand, the shadow disappears. Thus, since the LiveScope systems each have three elements covering one direction at varying angles, the shadow are not as noticeable, if they are present at all. Let me know if you have any other questions.

Me -
Why does Perspective show shadows, whereas Forward doesn’t?


Also in your reply you mentioned “3 elements”. I thought there were 5.

Garmin -
There is only 3 elements, as seen on the bottom of the transducer, you can see each line where there is beam / element for each direction. Forward, backwards, and straight down.


Perspective is just in a lot shallow of water to where in brighter conditions you will be able to see shadows, sometimes it can also just be reflection of the fish / object off the surface.

#1 makes sense, #2, I’m not sure.

Quote:

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Originally Posted by justinp61

#1 makes sense, #2, I’m not sure.

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I'm with you, Justin.

#1 explanation is more easily understood knowing that SideScan only uses 1 piezo on each side. Shadow's there because there's no competing signal from the other two piezos lighting up the area behind/below the fish, like there is on FFS.

#2 explanation just don't give me enough info. Now, if he'd said Perspective Mode only utilized the forward piezo, that might have made more sense to me. From what I've seen of LS in Perspective Mode, in videos & pics, I'm not so sure about the shadows being "reflections" (or even shadows caused by the Sun in clear, shallow water).

Besides ... when you're in FF Mode, what you see on the screen ... as far as "the bottom" ... shows as just a thin line. When you're in Perspective Mode the bottom is a wide swath ahead of you, because you're using all three piezos "sideways". :twocents

Concerning #1-
The example of the second flashlight shining in the back of the first doesn’t seem to hold true IF the shadow is cast in the same ”slice” as the object.

For example an upright tree-
The shadow cast at the very bottom of the tree would not be blotted out by any light from the next ”slice”, since the bottom of the tree and also the shadow at the bottom of the tree are in the same slice.

Imagine three guys standing a few feet apart, each with a flashlight, all shining on a 1 1/2" pipe 50' away. Think of it as bicycle spokes and hub, the flashlights are at the wheel, the spokes are the beams, and the target is the hub. There isn't going to much of a shadow because of the angles of the lights.

I'm still ruminating on #2.

Interesting topic.

Quote:

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Originally Posted by justinp61

Imagine three guys standing a few feet apart, each with a flashlight, all shining on a 1 1/2" pipe 50' away. Think of it as bicycle spokes and hub, the flashlights are at the wheel, the spokes are the beams, and the target is the hub. There isn't going to much of a shadow because of the angles of the lights.

I'm still ruminating on #2.

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Justin, aren’t you assuming that the beams (flashlights in your example) are focused on the same object? It is my understanding that LS using 5 or 6 beams are focused at various angles from the transducer. And the image we see onscreen are those individual beams that are stitched together.
Attachment 499078
If a number of beams (flashlights) were focused on a single object, your point may be valid.

What do you think?

Not so much one object, but one direction with the beams overlapping. Speaking specifically talking about forward view. I suppose the bicycle wheel wasn't a good example.

Quote:

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Originally Posted by DeadlyDan

Justin, aren’t you assuming that the beams (flashlights in your example) are focused on the same object? It is my understanding that LS using 5 or 6 beams are focused at various angles from the transducer. And the image we see onscreen are those individual beams that are stitched together.
Attachment 499078
If a number of beams (flashlights) were focused on a single object, your point may be valid.

What do you think?

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No, Garmin has already said there's only 3 piezos in the transducer ... each one has a 20* beam (45* angle) ... covering a 135* long & 20* wide swath of water. There are "shadows" in Forward Mode, but only under certain conditions & settings (see pic below):

https://i.ytimg.com/vi/-LWAgq_RDdg/hqdefault.jpg

You can see shadows of the school of fish at 8ft deep & directly under the transducer. What you're NOT going to see is shadows of individual fish in the distance, like you can with SideScan or LS in Perspective Mode. Those shadows get washed out by the lighting up of the bottom by the overlap of the sonar signal at distance.

Thanks, CrappiePappy! First time hearing the word Piezos. Looked it up, very interesting.

I want to learn, but need simplification. The math, “there's only 3 piezos in the transducer ... each one has a 20* beam (45* angle) ... covering a 135* long & 20* wide” is understood. Please help me understand the 5 or 6 “cone zones” in the image below. I have a curious nature and love learning. Wished I was more intellectual. LOL
Attachment 499093

Dan I will say that I've spent 1000's of hours using livescope and consider myself to be quite good at catching fish, but both of your deep thinker threads has got me thinking. I too have an inquistive mind. Scott

Quote:

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Originally Posted by DeadlyDan

Thanks, CrappiePappy! First time hearing the word Piezos. Looked it up, very interesting.

I want to learn, but need simplification. The math, “there's only 3 piezos in the transducer ... each one has a 20* beam (45* angle) ... covering a 135* long & 20* wide” is understood. Please help me understand the 5 or 6 “cone zones” in the image below. I have a curious nature and love learning. Wished I was more intellectual. LOL
Attachment 499093

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I would say the settings on this unit are set way too hot, for starters. Those 6 "lines" showing are a result of the "hot settings", sonar reflections, and/or what is called the "ghost tree" effect. And it could also be turbid water particulates being magnified by those reflections.

Another thing I found while searching for answers to your "shadows" questions is this :

there is a distinct difference in the software between forward facing mode and perspective mode on a fish finder, with perspective mode essentially offering a more detailed, 3D-like view of the underwater landscape directly in front of the boat, while forward facing mode provides a broader, flatter view of the area ahead, with different algorithms processing the sonar data for each mode to create these distinct visual representations; essentially, they are separate software settings with different functions.

Now, the important part of that statement, to me, is that there are "different algorithms" processing the data. So, with that in mind, you can see why there's little to no "shadows" showing in Forward mode vs Perspective mode. The functions of these two modes are completely different & thus are programmed to give you different views.

CrappiePappy
Thanks for the detailed information. Interested to know where you find the info. I’d like to read more. Can you supply a link for further reading?

The different algorithms seem to answer my question.

Quote:

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Originally Posted by DeadlyDan

CrappiePappy
Thanks for the detailed information. Interested to know where you find the info. I’d like to read more. Can you supply a link for further reading?

The different algorithms seem to answer my question.

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Dan, I'm certainly no expert (on anything) so I just Google stuff and put in questions about the subject, then if the AI version doesn't answer my question I'll check out the links that come up. If that doesn't give me a suitable answer, I'll change the question around a little to see if that brings me a better AI Overview statement or another selection of links to check out.

In this case I Googled: "is there a difference in the software of forward facing mode and perspective mode" (which is where I got the quote about the software/algorithms from the AI Overview)

And also Googled : "what causes the 5 lines eminating from the transducer in livescope" (where I got the "reflections" & "ghost tree" reference from the AI Overview)

I did Google other aspects of the question, but they've been replaced in my search history with other dead end questions & the two questions I just mentioned, so I don't remember the exact way I phrased those questions.

CrappiePappy
Thanks for the search tips. Anyone with a will mind can learn with Google. Could probably earn a Phd in a given subject if you stayed at it…

Only wished AI would give the resource(s) it used to compile the answer. I looked a didn’t find that.
UpDate - just discover the “link” icon at the end of the section does bring you to other information. Although it doesn’t seen to give references for all of the info.

The way the software interprets the data in the Black Box and then presents it on the display must make the difference in the unique views between FFS and Perspective. Perspective looks like 3D and FFS is flat.

I find it interesting that the FFS cone is 20 x 135 degrees and the Perspective cone is 150 x 20 degrees. Same transducer, one 135, the other 150.

Quote:

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Originally Posted by DeadlyDan

The way the software interprets the data in the Black Box and then presents it on the display must make the difference in the unique views between FFS and Perspective. Perspective looks like 3D and FFS is flat.

I find it interesting that the FFS cone is 20 x 135 degrees and the Perspective cone is 150 x 20 degrees. Same transducer, one 135, the other 150.

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I see Perspective's cone angle quoted as 135* AND 150* ... depending on where you look. Like you, I'm not really sure why Perspective mode would show a 15* wider span.
Even Google AI Overview says both are 135* in one instance, then says both are 150* in another instance, and 135* for Forward & 150* for Perspective in other instances. :Doh:

So ... who knows :dono

The only way I can see Perspective having a 150* span is if the software allows it.

Below are a few replies rec’d from knowledgeable YouTube publishers.

FloppingCrappie -
LS Forward will show shadows on larger objects near the bottom, typically large trees and birdge/dock pilings, but only when the transducer is pointed at a specific angle and only on the bottom of the screen. The sonar beam for livescope is technically still being stopped (producing a shadow) on fish suspended in the water colum, but unlike sidevu, there isn't anywhere for shadow to appear on the screen. If you were to scan a school of fish that were suspended 10ft down in water colum, but had a background like a concrete sea wall or large bridge piling, I believe you would see the shadow of the school of fish.

Randy Carpenter with Garmin Guru -
The shadows show up on the bottom. If you were scanning a bluff wall then they would show up on the bluff wall.….In another reply he said -
Because the bottom is shown in q 2 dimensional way whereas Perspective is more 3D due to beam angle.

I rec’d this from a Garmin Tech. The bright bottom seen in Perspective makes a lot of sense.

”There is only 3 elements, as seen on the bottom of the transducer, you can see each line where there is beam / element for each direction. Forward, backwards, and straight down.

Perspective is just in a lot shallow of water to where in brighter conditions you will be able to see shadows, sometimes it can also just be reflection of the fish / object off the surface.”