Topic: The Proof of Humminbird Down Imaging

[DougV]

A buddy of mine Mike Bucca performed this test. We worked for several days trying to figure out how we could prove the theory of Down Imaging and Fulle Coverage of SI. This test Proves it:

After all the "hoopla" about Down Imaging and questioning whether Down Imagingg scans directly under the boat I thought of an experiment that would prove without a doubt that the the DI IS TRUE Down Imaging.  Let me first go backwards a little bit with some images that have already been posted and then I will move towards my experiment. 

Nobody knows 100% for sure what is inside a SI ducer except for those @ Humminbird and anyone who has personally cut one open. Does it strictly have 2 beams?  Was Humminbird creative enough to have a 3rd beam inside with the intent of doing down imaging?  I don't know the answers to these questions but read further and see if it matters based on the images below.

We started off with this SI image.  This is based on the "theory" that Humminbird uses 2 crystals and creates down imaging from these two crystals to get True Down Imaging? 

The Proof of Humminbird Down Imaging

If you look at this photo above you can see that I split the trunk of a good sized tree AND it's limbs all the way to the tips which as you know are much much smaller in diameter.  It was also "theorized" that there is a weak signal at the edge of the DI beams.  In this photo there seems to be NO weak signal which is proven based on the crispness of this image above.  If there was a weak signal it would be blurry on the leading edges and you probably wouldn't be able to pick out the seperate limbs...

An argument was also made that this tree was "massive"  So enter exhibit "B".  A smaller tree. 

The Proof of Humminbird Down Imaging

Again split right down the middle and it's limbs matched by the adjoining red lines. So if in fact there is a gap or weak signal its surely not shown in these side images as the limbs and trunk is again clearly shown.  I got 50 different images of where I have cut tree trunks and limbs in half with Side Imaging so I won't bore you with excessive images.. 

So even with those two images and many others that were presented by Doug and myself I wanted to take it a step further.  So lets take a KNOWN SMALL target and see what we can do with it. 

The Proof of Humminbird Down Imaging

Here is a balloon.  It was blown up to roughly about the size of a volleyball.  It is approximately 7 inches across.  It is anchored by a milk jug full of rocks with twine and a bouy to above it which marks the spot on the surface.

So all I had to do was run over the bouy to try my hand at SPLITTING a Ballon in half.  I was careful to take the boat out of gear to prevent it tangling in the prop as I heard the bouy slide under the hull. 

The Proof of Humminbird Down Imaging

The math is 3.5 inches is HALF of 7 inches the width of the ballon.  Can I get 3.5 inches of a balloon on either side of the SI beams AND have it show up on SI, DI and 200khz sonar??  Here is the cross segment of that experiment.


The balloon is approximately 15ft from the bottom and it WAS SPLIT in half by the SI beams (3.5 inches on each side) and it did show up on DI and 200khz (20 degree) sonar.... 

Here is a bigger image of the screen shot.

The Proof of Humminbird Down Imaging

and just in case you think I got lucky  :wink:

The Proof of Humminbird Down Imaging

I got plenty more images where the balloon has been split and others with 200hz, 83hz, 200/83 sonar split with DI etc etc..  This one below shows that I had the sensitivity on just 12.  Just a little over half way which means I still got more JUICE to spice up the image. I bet I could have easily gone to 10 and still see the balloon.

The Proof of Humminbird Down Imaging

Here is proof in the pudding and what it all boils down to..

The Proof of Humminbird Down Imaging

Having done the test above proves that there is solid coverage below the boat.  Knowing how to get quality images and basic tuning of your machine is part of getting the most out of your unit.  If your unit can't do this simple test call Humminbird customer support @ 1-800-633-1468

Enjoy your FREE TRUE down imaging .  I know I am

Mike

[RGecy]

Doug,

Glad to have you over here on the forums.  I have been trying to make this point for months!  Thank you so much for such an intutive post.  This shows without a doubt that the coverage is 100% (or damn near it)!

I look forward to seein more post from you!

Robert

[Jolly Roger]

Wow Doug,
that is one hell of an article, thanks a ton!
As we say over here "a picture tells more than thousand words", this is truly showing in your post.

I really like the test setup and the results even more. Makes me also a bit jealous seeing some going out on the water, while I have the boat in winter storage.  Can't wait to go out and play with my 981.

Thanks again and greetings from Germany
Harry

[Rezfisher]

Great pictures, can't wait for ice out.

JIM

[soretoe]

Welcome Rezfisher. Glad to see that you have joind us. Hope to see you more often.

[john stephens]

thanks for the article and the information its was nice to see. john

[mrj9600]

Great article. Gives a lot of info.
/Martin

[George]

DougV

Welcome Doug, your overview is great.  This is one for my archives, I have copied this so that I have it for reviewing over time.

Looking forward to your insights.

George

[fishbone]

Thanks for the amazing tests.
Do you think the DI would show the balloon if it were held to the bottom, rather 10' up in the water column?

[wizzo86]

Great job Doug! Welcome to the forum. Looking forward to your imput. We all know how great humminbird's SI is. Now everyone that visits can see it for themselves. Great Job!!!

[mirb]

Great job! Do you think you get the same result with the balloon 1ft up from the bottom?

[DougV]

First off I was some of the brain power behind this test but Mike Bucca from Georgia collected the data and photos. We have been challenged on several public forums about our knowledge and about SI and DI. We knew it what it would do... I forgot to mention that Mike performed the tests...Guess I was so excited to show the results as I thought would happen.

But I have seen Full Coverage from SI for many years in screen captures:

Like this one I split these willow trees:

The Proof of Humminbird Down Imaging

This photo you can see the trees prior to flooding when the water was in the parking lot here:

The Proof of Humminbird Down Imaging

This Bridge that has exact duplicate scans on both sides of the screen:

The Proof of Humminbird Down Imaging

I like to say the "Proof is in the Pictures"

[RGecy]

I cant believe none of the divers on the board here even said anything (including me), but since the balloon is filled with air, it will compress under the pressure of the water.

At 15' the balloon would have been roughly 2/3 its original size of 7", which would have made it about 4.6".  Even more proof!

Robert

[Triton Mike]

Defintely a joint effort .  Doug had some good input as we planned this experiment. 

First off I was some of the brain power behind this test but Mike Bucca from Georgia collected the data and photos. We have been challenged on several public forums about our knowledge and about SI and DI. We knew it what it would do... I forgot to mention that Mike performed the tests...Guess I was so excited to show the results as I thought would happen.

But I have seen Full Coverage from SI for many years in screen captures:

[sonar2000]

Doug.  thanks for the pictures.  could you send me a copy of the recording for the bridge.  I would like to play with that a bit.   chuck  (sonar2000)

[Jolly Roger]

Defintely a joint effort .  Doug had some good input as we planned this experiment.

Welcome to the Forum Mike!
And my respect to you as well.
I wonder who ever challenged your wisdom, but I guess they are silenced after this test.
As Robert correctly mentioned the balloon was even smaller due to the water pressure. The better the result!

I posted some of my findings here in the forum:

http://forums.sideimagingsoft.com/index.php?board=56.0

For me it was very impressive what details are visible on the screen of my unit. Diving down and have a direct comparison makes it much more obvious that the Birds are able to show what's going on down there.

Now I'm curious and eager to go out and play around with DI, the new colors and all the other goodies.

Regards and thanks again for the test!
Harry

[Kimi]

Hi folks!

If this is thrut, it would be great. But I think some more tests should be done before we can say hiphurray! Take for example that picture of the bridge. If the both halfs of the picture are exactly identical, there meight be something wrong.
 
In the balloon test, the balloon should be put on the bottom, and see whats happend.

One explanation is that somthimes you can get so called "ghost echoes". That happends when the signal hits an hard an clear surface such as rock or steel on one side, and if the opposite side is empty. I have seen this happend several times. But dont ask me why it happens!
 
There is still things to be explained and understod, and one must be openminded if we are going to learn new things and going forward. Thats why its so facinating! Sorry if Im sceptic. Thats just the way you get, when playing hundreds of hours whit theese "toys"! 
 
Well my boat is covered whit 3 feet of snow, and the northern Baltic sea is covered by ice. So I cant go out and make testdrives, looking to the screen "from an new angel".     ( Where did that global warming dissapeard??)
 
If you look at the picture bellow. Tell me is the cursor right under the keel line or is it 20 meter on the right side of it. Think about it !
 
Kimi  (Finland)
 
 
 
 
 
 
 
 
 

[keizerh]

19 metres on the right side

hendrik

[RGecy]

Here is one that I think definitely shows that the beam covers 180 deg.  Yes there has to be a small gap, but it is very minimal!

The boat was lying on its side and the log speaks for itself.  Two examples in the same image!

Robert

[George]

The pics really tell it all, not only for downimaging but that we are also seeing directly under the boat.

Thanks to everyone for the pics.

George

[Kimi]

- Ok.. I think its time to chek out if there is som difference between 1000,900,800 and 700 series Humminbird sidescanners! Just to be shure that we are talking about the same thing! One is talking abouth the mother and one about the daughter! 

I wonder if the line between the black area and the visible area really is the keel-line. If the sonar has full coverage, it should be. So, can anyone explain why the cursor mark on my greyscale picture, thats on that line, is actually 20 meters (60 feet) on the right side. I have dived and scanned that wreck severall times, so Im shure that the cordinates, marking etc. really works. Normally "target accuracy" is about 7-8 meters ( 15 ft) in 15-20 m deep waters. And I think Humminbird is really doing a good job when locating, and giving cordinates to underwater objects!

Kimi..!

[sonar2000]

for the 1197 units. If indeed the si scan for 455 khz is 86 degrees wide that will leave a down under the boat 4 degree which is usually depicted by the dark part on each side of the si image. depend in the depth of the water this left and right area under the boat, which may or may not be displayed will vary.  It is a matter of angles and in math it is figured as the tan of angle B is equal to the opposite side divided by the adjacent side.  To calculate the adjacent side (which is the area directly under the boat we will figure adj = opposite divided by the tan of angle B  .  ok so far.  now remember that any thing sticking up from the bottom directly under the boat may be or could be in the shallower cone. This will show up in the display where it enters the cone.  I will try to make a picture of this and get it posted.  chuck

[kosmo]

http://www.xumba.scholleco.com/viewtopic.php?t=2359

[RGecy]

Kosmo, Great pictures.  I went ahead and uploaded them here since we have the same discussion going.  You also have the ability to create your own Personal Gallery, Personal Pages or Customized Profile here on the forum.   Let me know if you have any questions on how to do this.

Great work!

Robert

[CFDCar27]

Good Images, I often use a weighted marker with a topside float to give me a good reference on the surface. The weighted box is 2’ cube made out of PCX and covered with screen wire. It lights up when scanned.  You have giveme some new ideas when using the down looking image. I have not added the new upgrade to my units but plan on doing it shortly. Does it take long to so and do you lose any of your old data or settings.

thanks, jd

[Jolly Roger]

Hello JD and welcome to the forum!

Updating your units shouldn't take long. Robert posted a "How To" here:

http://forums.sideimagingsoft.com/index.php?topic=12.0

For the settings and data, I would suggest to export all nav data to your sd card and store them for back up on your PC. Write down the settings to make sure you have them somewhere. The unit will reset to factory defaults automatically with the new update.

I like your idea about the screen wire covered marker! Thanks for the information. I'll give this a try when I'll be able to get out on the water.

Regards from Germany / Harry

[IRC Kevin]

Hi folks!

If this is thrut, it would be great. But I think some more tests should be done before we can say hiphurray! Take for example that picture of the bridge. If the both halfs of the picture are exactly identical, there meight be something wrong.
 
 

I think I understand what you are getting at here, Kimi. The pictures all look like mirror images. Is it possible that the HB does have this blind spot of x degrees below the boat and actually takes the nearest image from either left or right transducer side and cuts it to look like a bisected target?

I've just reviewed one of my deep targets in Humviewer of a known wreck (25 feet long by 8 feet wide), which has been neatly split in half by the HB. If there is anyone good at the maths, perhaps they can make more of this with the Lat/long coordinated I took from each side of the bow.

Left Transducer- depth 63.9 metres. 54 degrees 23.840 N, 2 degrees 57.181 W

Right transducer- depth 63.9 metres, 54 degrees 23.844 N, 2 degrees 57.063 W

The target was this one (screenshot off HB)

The Proof of Humminbird Down Imaging

[IRC Kevin]

Just to throw another possible spanner into the works- this was one of my earliest goes with the HB. I passed about 20-30 feet to the port of a racing buoy. The image of the bottom weight only appears on the right view, but appears to be virtually under my boat.

The Proof of Humminbird Down Imaging

[RGecy]

IRC Kevin,

This is a great example of how an image can appear to be in the water column below the boat but is actually out to the side.

This has some similar examples.  http://forums.sideimagingsoft.com/index.php?topic=715

Robert

[Teberd]

In the pics with the balloon (if that is the balloon), where is the milk jug ? It would seem that either the Si or the DI would have shown the jug as well since the jug is bigger and does not collaspe like the balloon. Just sayin. I have a 997 and not trying to dispute the test, but I just haven't figured out the DI or how to interpret the views of the DI. When I think of DI, I tend to wanna think of sticking my head over the side of the boat and being able to see the object from an over head view, but every image I have seen on mine appears to be similiar to a side view of the object. Could somebody attempt to explain this or at least correct my may of thinking ?

Thanks
Tracy H

[RGecy]

Tracy,

Welcome to the forum.  Here is another image posted by Triton Mike of the balloon showing the bucket. 

Basically Down Imaging is nothing but Side Imaging in a verticle or traditional 2D view.  The two SI images are combined and filtered to give you the view under the boat.  Some people have a harder time understanding SI and for them the DI is more of what they are use to with traditional sonar.  I think there are some very good advantages to DI, especially for fishermen, but as I have stated before, you really are not gaining any new data from the DI view.  If you understand how to read SI, then all the data is already there and you can actually gain more info from the SI.  I will have to elaborate more later.... 

I have got to run for now and do some real work!

Good luck and again, welcome to the forum!

Robert

The Proof of Humminbird Down Imaging

[littleman]

how long will take to learn what you are looking at ,we were catching fish like crazy and my new 798 did not show any under the boat  .we tyred dropping thing down beside the boat and never could see any thing . we try ed anchor .jigs rope and never see any thing . what are we doing wrong.

[littleman]

where can you see or buy a video on using the new units such as the 798

[Hammer]

Okay, I was not sold on this theroy until the last image was posted.  Now, with that said, the anchor does not show up in the original post.  Being that I am involved in SI in the aspect of Search & Rescue, DI is very important if it can be incorporated with the SI scanning.  What, if any manipulation was done from the first to last image?  Was this able to be seen on the live scanning or could this only be seen while reviewing the recording on a PC?

BTW: Thanks for the detail drawing on the last image, for me atleast, it showed me how to inturpret the image and understand HOW to recognize what I am looking at.

Thanks,
Hammer.

[AHL]

After read this entire thread and the write up of HB's DI  I also find it a bit odd that the milk jug wasn't seen in the first images. It could of course be hidden in the "weak spot" right beneath the boat.
Anyway, from my experience  recording with the 1197 and especially after a good georef and Mosaic processing the SI is covering almost everything in the 180 deg - so yes it is fair to say that it does DI. However, what I do have a problem with is the DI view in the HB unit - I haven't seen a good explanation (yet) on what we actually see on the screen and how the left and right SI data are  merged into the odd "side way" DI view.

[sonar2000]

AHL, I have wondered since the release of the DI.  From review of a number of recordings I feel that the DI is strongly influenced by the Left SI return.  I can see targets in the Right  SI, but they do not show in the DI.  No words of just how the DI is produced so we will have to await for a good explaination of the return display. 
A very good question and I too would like to know exactly how the DI is determined. 
Chuck

[countryboycansurvive]

This, I assume, is an old collapsed stone fence wall.  It's near an old plantation home which typically used these type fences years ago.  Obviously I crossed it on a diagonal line but the down image indicates the fence forms a corner at a narrow angle.  I think the down image is simply the side images folded together with some of the shadow detail removed.

[Moose1am]

Well I have been scuba diving since the early 1970's.  I also am an EPA Air Pollution Specialist and very familiar with the Gas Laws long before I started scuba diving.  Had to learn about Boyle's and Charles's laws in HS Chemistry and Physic's classes.  Had to study those laws again when I was in College as I took a few more chemistry and Physics classes at Purdue University.

I have been using sonar since Lowrance came out with the "little green Box".  I hide the little green box inside a black bag back in early 1967 when I was just a sophomore in HS and fishing Kentucky Lake with my dad.

I am technically orientated and enjoy reading the manuals and figuring out how thing work and why.

Now, we all know that if you try to shoot the transducer's sound waves though air they won't go very far at all.
 
Air does not transmit sound like water does.   We all should know that if you put a transducer on the bottom of a double hull boat it won't work very good or won't work at all.  And even on a single hull boat you have to epoxy the transducer to the bottom of the boat and get all the air bubbles out of the epoxy so that the sound waves will pass though the epoxy and boat hull and down into the water column and back up again to the transducer. Air bubbles in the water can kill the sound waves.  Always place the transducer in laminar water flow.

Not sure that a balloon is the best target other than it's buoyant and will hold up the rope straight above the bottle of rocks.   

If I were doing this experiment I would add something like a metal trash can lid above the balloon. The metal trash can lid could have a hole drilled in the center and then feed down the rope where the balloon would hold it up off the bottom.   The metal will reflect sound waves much better than the thin skin of the balloon.  Also the air inside the balloon may or may not reflect the sound waves back up to the transducer.  The shape of a balloon being round won't reflect all the sound waves back to the transducer above.  Some of those reflected sound waves will bounce off in other directions.

And finally something I picked up by playing a Submarine Simulator game called Dangerous Waters.

Today's modern nuclear submarines use sound to see whats around the sub when it's underwater.  They use Towed arrays to listen for the sounds in the ocean.  The towed array reminds me of a towed side scanning unit in many ways.

Once thing that I learned to do when interpreting these sonar returns was to eliminate the false echo on the sonar Broad band sonar screen.  As there are two images that are 90 deg apart and you have one that's real and the other is a false echo.    I wonder if that's applicable to SI screen of these trees and the balloon?

I'd like to see the boat go to the right side of the balloon by about 50 ft and see if the image of the balloon only shows up on the left side of the SI screen.  Then cut the distance in half and go 25 ft.  Making another pass and go only 10 ft and then 5 ft and then repeat it a few more times going to the Left of the balloon instead of to the right side. 

If anyone remembers the 3D sonars that Humminbird built about 10 years ago. They were part of the matrix units. They used a phased array type sonar transducer that would send the sound waves out in different directions in a phased array pattern.  This way the computer showed the bottom in 3D on the 2d screen.  I remember when Humminbird first came out with those and I wanted one very much but could not afford to buy one.  But I kept my eye on them until they stopped making them for a few years. They did make a come back but not sure if they are still around anymore.  SI has basically taken over from the old 3D type units. 

But the point is this. Humminbird knows how to make a phased array type sonar transducer.  So I'll bet that the new SI transducers can have their sound waves focused in different directions using the computers inside the control heads.  That's why they were able to make the newer transducers do Down Imaging as well as Side Imaging with only a software change to the control heads.    They did this already ten years ago.

I cant believe none of the divers on the board here even said anything (including me), but since the balloon is filled with air, it will compress under the pressure of the water.

At 15' the balloon would have been roughly 2/3 its original size of 7", which would have made it about 4.6".  Even more proof!

Robert
[/qu

I cant believe none of the divers on the board here even said anything (including me), but since the balloon is filled with air, it will compress under the pressure of the water.

At 15' the balloon would have been roughly 2/3 its original size of 7", which would have made it about 4.6".  Even more proof!

Robert

[AHL]

Countryboycansurvive,
Good that you posted that Humviewer snapshot - it prompted me to compare the views on the Humviewer and the 1157.  The good thing is that the DI presentation looks the same. What I do find a bit strange and what also makes me question the usage of the DI view is the following: (I'm using your snapshot as the example).

The fence that can be seen from the left side SI shows up first on the DI screen. When the boat crosses the fence it starts to show on the right side SI (because of its angle to our direction), and from that we can tell it's direction. Looking at the DI we can see that it is combined of the left and right from the SI, but there is no way you can see what is coming from the left or right side of the boat. It actually looks a bit messy - doesn't it ?

So is there any advanced processing ongoing to generate this view, does the view even make sense ?  Sorry guys - nothing like that. I did a quick test with photoshop and overlaid the left SI on the right SI (just had to mirror the left SI and set opacity to 50%) and voilá I generated a picture that is almost identical to the DI view image.

in most cases the DI view doesn't add any information, on the opposite it generates a picture that at least I find more difficult to read.

For me a DI view would better be a view with the water column taken out, similar to what you get with a mosaic post processing.

Anyone from HB who would comment this??

[RGecy]

Well, you guys are finally seeing what I said long before DI was even released! 

I think Down Imaging is great for the guys who are having a hard time reading and understanding the Side Imaging initially.  It has the look and feel of a traditional 2d sonar view but with a lot more detail, and that makes it easier to comprehend.  Very Cool right!  But what you are forgetiing is that by going back to a traditional singular down looking view(just like a 2d view), you eliminate any reference of left or right. 

For example.  What if an object is just off to one side of the boat sticking up off the bottom?  Of course it shows up in the water column and of course shows up in DI view?  even though its fairly close to the boat, its not directly under the boat.  But how do you know?  If you are not looking at the SI view, you would not be able to tell if its on the left or on the right side of the boat at all.  Your basically guessing which side to cast your line and try to hook that big fish you saw suspended in the structure! If you were looking at the SI view, you would know immediately left or right.

So then the question beomes, if I have to reference SI anyway, and DI is nothing more than a composite of SI, why am I even looking at DI?  

Again, don't get me wrong, I think DI has a place in the fishing community.  But in the end, I think once you learn to read Side Imaging and truly understand what you are seeing on the screen, you will be using Down Imaging less and less.

Robert Gecy

[mendota]

To further emphasize Robert's statements - DI is really just a high resolution conventional 2D sonar view, not an actual "down image".  The pretty DI pictures you see posted are due to accidents of geometry and are highly misleading.

As such, for DI it is the information in the water column that is of interest, not beyond the 1st bottom echo, where the info is muddled, as you have all noted.

DI is showing a very narrow slice of the bottom, rather than a cone.  Use this to advantage - the one situation I have noticed that DI works well is in separating fish from the bottom in fast drop-off areas, where conventional 2D sonar is blinded by the slope.  You can literally dissect a dropoff with the DI, if you are traveling perpendicular to the break.

Of course, as Robert said, the same information is in the SI view, just in a different format.

[drfish]

Observation 1:  After having my unit for a whole 2 weeks, but looking at quite a few images, I am really at a loss for what DI adds other than as a counter for the competition's marketing gimmick.  I looked at Halfen's side by sides of SI and DI of the fish cribs on his local lake and what I see is merely the elimination of anything lateral to the bottom of the water column.  It adds nothing from an information standpoint, except that I suppose your resolution is a bit better because of the size of the image. 

But if you take a look at the Haflen images you can compare the image starting at the top of the SI waterfall on the port side image looking at the bottom return closest to the midline and compare that to the bottom return of the DI image reading from right to left.  They match perfectly, of course.  My point is that what information is there that isn't in the SI image?  However, there is a lot in the SI image that isn't in the DI image.
Then again, I'm just a noob.

Observation 2:  Shouldn't there be some shadowing from the balloon since the sound shouldn't transmit properly through the air?  Also, If you look at the return that is labeled as the balloon, there are two small ghost echos between it and the bottom.  Curious what the likely cause of that would be.

[situskak]

What a great pictures!
SI and DI become  more interpretable.

If someone try to do same thing  with real fish instead of balloon,
it will be much better.

Tac

[RGecy]

Tac,

The problem is getting the fish to pose for the image! 

Robert

[DougV]

You have to use "Stunt Fish" and they were on strike and too expensive to hire... Ballon was used so the tests could be without a moveable element so it could show the differences.

Down Imaging does have some features like looking vertically how items are stacked in the water other than that all the data in SI is the same thing you can see in DI just have to learn how to read the view.

[Thani]

Hi Guys,

Thank you for the interesting topic. Whether DI is a composite of SI or not, I find it useful especially when trying to anchor on a wreck for diving. We use to do this with standard 2d sonars but the traces of fish schools make using 2d sometimes challenging. With the clarity of DI you are sure will not miss the wreck. Anchoring with SI is quite impossible. This is important for divers especially if visibility is not that good like where I live (Dubai, UAE). Because if you do not anchor correctly you are likely to miss the wreck and thus waste the whole day trip and the fun.

I tired searching for the best settings for both SI and DI but no luck, we need to establish such info and anchor - make it sticky - it at the top. can you guys do that please?

Thanks again,

Thani