Sonar Target

[richie conroy]

archaeology was the word i was looking for thanks Ric

Sorry for putting these question's here an now, however my kids have always asked why i spend my evenings looking at rocks underwater

And this subject i thought would quell there questions, How naive was i, Now it's were when an how

Thank's Richie

[Walt Holm]

Hi Ric:

   Here is what I meant by the classic "waterfall" stripchart display.

  A sonar mosaic tries to put everything into a nice 2-D display but in the process hides a lot of the details about how the sonar beam is impinging upon the target.  The waterfall display preserves all of the original information about the sonar beam.  What you can't immediately see on it is where the AUV is (GPS coordinates), what the heading of the scan line was, and what the speed of the AUV was (i.e. scale in the vertical direction).  Like you say, you need the software that comes from the manufacturer (EdgeTech, in this case) to pull out those details.  But this is a case where you should really be looking at the raw data, since you have no idea looking at the mosaic what the computer has done to "adjust" the picture.

  For instance, if the AUV navigation was set to overlap it's scan strips (this should have been done), then, depending upon the amount of overlap, it's either possible or quite likely that there are two different sonar images of the anomaly, taken at different angles.  The mosaic software throws out much of this data in order to present what it assumes is a nice 2-D picture  of the seabed.

-Walt

[Ric Gillespie]

   Here is what I meant by the classic "waterfall" stripchart display.

Ahh...thanks Walt.  The screen shot of the anomaly from the .csf file that I posted on May 16 is actually from the "waterfall" strip chart.  I rotated it to make it more understandable.  I've attached it here in it's original orientation.

A sonar mosaic tries to put everything into a nice 2-D display but in the process hides a lot of the details about how the sonar beam is impinging upon the target.  The waterfall display preserves all of the original information about the sonar beam.  What you can't immediately see on it is where the AUV is (GPS coordinates), what the heading of the scan line was, and what the speed of the AUV was (i.e. scale in the vertical direction).  Like you say, you need the software that comes from the manufacturer (EdgeTech, in this case) to pull out those details.  But this is a case where you should really be looking at the raw data, since you have no idea looking at the mosaic what the computer has done to "adjust" the picture.

Yes.  The sonar expert (I'll see if I can get permission to release his name) who examined the image had all of the raw data.  His opinion, after several days of working on it, was:
"I looked over everything and agree that your missed target is viable and should be checked out.  Very probably a manmade object.  Only other option is that it is a rock ledge but it doesn't look like the other ledges seen from the entire SS mosaic."

In fairness, another expert who has not yet examined all of the data feels that it's "probably geology."

The ROV pilot I sat beside for day after day as we checked out sonar targets feels that the target looks "VERY promising, definitely NOT a rock."  His full response is priceless but I need to get his permission before I can share it.

We're still casting the net for opinions but, as one expert pointed out, interpreting sonar imagery is an art, not a science.

  For instance, if the AUV navigation was set to overlap it's scan strips (this should have been done), then, depending upon the amount of overlap, it's either possible or quite likely that there are two different sonar images of the anomaly, taken at different angles.  The mosaic software throws out much of this data in order to present what it assumes is a nice 2-D picture  of the seabed.

You make a good point.  The runs did supposedly overlap. There should be a second image buried somewhere in the data but finding it could be difficult.  The raw data is not organized in any way I can make sense of and I can only read the files that were rendered as .bmp.  It's becoming apparent that the original contractor dropped the ball big time. I can get an assortment of experts to give us quick opinions on specifics but it may be that what we need is for someone with the software, knowledge and experience to really spend time digging into all the data to see what we have. That's going to cost money - money that we don't have right now.
   

[Greg Daspit]

If the big shadow has what may be windows, would they have to be broken?

[Ric Gillespie]

If the big shadow has what may be windows, would they have to be broken?

I don't know, but based on other Electra wrecks (on land) the shell of the fuselage is quite fragile and tears open easily.

[Greg Daspit]

One detail that shows up in the hi def image Ric posted (in reply 35) is what looks like some vertical and parallel lines at the upper right corner of the big shadow. They could be exposed ribs/ frame pieces.

[Randy Conrad]

After seeing the latest sonar target pic file, I just remembered something that I think may become useful. Several years ago Ric, my uncle had done some training with NASA. My uncle works for a private government firm that deals with making maps. Anyway, while doing some training at NASA he inquired some lunar maps that were made into a 3 dimensional hologram per sorts. At first you didnt see it just looking at the sheet in front of you, that is until you held it flat, bout two feet away, and at eyes level with the paper. Anyway, when you held the paper out in front of you, the craters and the rocks came to life. It was really neat. So, I'm asking if Jeff knows about such technology and is it possible to use that technology on this so called anomaly photo. Therefore, if it is what everyone is saying...it will truly come to life. Something to look into!!!

[Jerry Simmons]

I certainly wish I could see what you folks seem to. I would like to, but I can't make anything out of the images. Could someone give a hint (such as was done with the Bevington object) to make us blind folks see what is there?

[Ric Gillespie]

I certainly wish I could see what you folks seem to. I would like to, but I can't make anything out of the images. Could someone give a hint (such as was done with the Bevington object) to make us blind folks see what is there?

I can (and will) put together an illustration of what I can imagine MIGHT be there.  Others may feel inspired to do the same -  but bear in mind that, unlike the Bevington Object, we're not dealing with a photographic image.  A sonar image is a reflection of sound waves and much trickier to interpret.

[Dan Swift]

I found this sonar image of a Beach Baron at only 56 meters.       

[Ric Gillespie]

I found this sonar image of a Beach Baron at only 56 meters.     

Very interesting. Note that the wing ribs are visible through the skin.  That's not unusual and it's why we were initially excited about the "wing" target that turned out to be almost certainly ship wreckage.
Note also how the side of the fuselage is illuminated and how irregular the shadow is.  Fascinating.  It would be great to see a photo of the wreck on the bottom to see how it compares to the sonar image.

[Dan Swift]

Couldn't find a photo of it on the bottom, found one after they pulled it up....pretty mangled.   It was reported that it was updaide down on the bottom.  No way to know that from the sonar image. 

[Greg Daspit]

I certainly wish I could see what you folks seem to. I would like to, but I can't make anything out of the images. Could someone give a hint (such as was done with the Bevington object) to make us blind folks see what is there?

Attached is a pdf with an illustration of hints I see so far.

[richie conroy]

Hi All

Thought i would post this link to some side sonar images  :)

http://www.enviroscan.com/html/gallery.html

Thanks Richie

[Chris Johnson]

Most of those excellent pictures look like there on a 'flat bed'.  Isn't ours on the side of a sea mount?