Welcome, Guest
Username: Password: Remember me

TOPIC: Editing in Sonar viewer

Editing in Sonar viewer 9 years 11 months ago #2502

  • Mats
  • Mats's Avatar
  • Offline
Hello again Matt,

I recently discovered that my first ReefMaster-made chart wasn't entirely correct. It had some curious bottom constallations that did not exist in real life.
So I began investigating my sonar log files, and it appeared that my early log files indeed had some mysterious errors.

They are all made with an earlier version of HDS software, and they all looks fine for a while, but then suddenly the "Primary" track gets out of phase compared to the "Downscan" track. See attached picture. I guess this depends on some bug in the earlier HDS software.

Anyhow,
Now I have to edit all the old sonar logs and remove the bas part, and then I realize how time consuming this is, Since I have to remove the tracks and points from the Track window. So my suggestion is a similar editing function in the Sonar window. Then it would be possible to delete an entire serial sequence without risking interfering and deleting good tracks.



I am also curious, the new "Sidescan module" that you have been talking about. What exactly will it do?
Will it create a graphical bottom chart similar to the one in the HDS?
Or will it simply utilize the side scan data to create better coverage and resolution for the current chart type?
Or have I got it all wrong?!

Cheers
//Mats





The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2503

  • Matt
  • Matt's Avatar
  • Offline
Hi Mats,
Those are interesting errors in the depth - I haven't seen anything quite like that before.
The depth editing is a bit basic at the moment in RM, and a multi-select as per your suggestion would be a good idea. Not sure we will get it in the next release, but I will note it.
The next release will include an update to the way track data is displayed in the map definition view, and it will be possible to delete track-points directly from that view. This will make it easier to find bad depths with respect to other tracks. Also, the depth "redrawing" in the sonar viewer will be much faster than it is now.

The sidescan module will produce mosaic images from sidescan data - so similar to the structure overlay in the HDS. There will also be a lot of improvements to the sonar viewer (see image below), with multi-channel display for both HB and Lowrance and functions such as accurate waypointing and measuring in the sidescan view, as well as optional slant-range and gain adjustment.


The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2504

  • Mats
  • Mats's Avatar
  • Offline
Hi,

Yes, the errors are indeed interesting, and strangely enough I have not been able to find anything about this on the web. And Lowrance is unfortunately not too public with the bug record, so I cannot be 100% certain that it was a bug causing this, or if it was me doing something wrong. But since I have the same phenomena in several sessions, I bet it was a bug. I don't remember the HDS software version when I made those tracks, but the unit was freshly from the US in June 2013.
If you are interested in looking at a file for yourself I can send it to you.


Thanks for sharing some info regarding the sidescan module. Sounds very interesting and promising. It will be a perfect tool for pre dive planning, bottom surveys and even for SAR. I will defenitely purchase the module when it becomes available.

But wouldn't it be possible to also use the data from those extra channels to enhance the functionality of the RM? I mean, instead of using the standard transducer for only vertical depth data, wouldn't it be possible to use the sidescan data to cover a much wider area? Or will it perhaps be possible to make a bathymetric chart out of the "structure overlay"?

The reason I ask about this is because I see at least two different user scenarios. One is as a pure survey tool where you would like to see a photo-like picture of the bottom. This is definitely cool, but perhaps not so useful for fishing. So as a fisherman, then I rather like to have a very accurate traditional bathymetric chart, and that is where I beleive the sidescan data can be a useful asset. Though, I have no idea what data Lowrance allows you to extract from the SL2 file, so maybe this is not possible at all.

//M
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2505

  • Meggs1
  • Meggs1's Avatar
  • Offline
I have also experienced this error on more than one occasion. It did not seem to happen all the time (even on the same sonar log recording). I'm not sure if it was the HDS Gen 1 or the Gen 2 that showed these effects.

@Mats
I notice you are using the Downscan channel. Is the same issue obvious on the Primary and Sidescan channels?

I also occasionally get a vertical shift during a recording i.e. the recording faithfully tracks the bottom for a while and then seems to shift above the bottom up to a metre and eventually goes back to following the seabed accurately. Consequently I have had to extensively edit my sonar logs.
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2507

  • Mats
  • Mats's Avatar
  • Offline
Interesting to hear that you have had similar issues Meggs.

I am normally using the primary channel when I work with the data and make bathymetrical charts. The downscan channel was just a way to verify the primary transducer data.

I have attached some screenshots from a different run. Now you can see all three channels from the same moment. The data is good until the marked point, and from that point and on it really goes south!
It is also quite clear that something is wrong when you look at the track window to the left, and see all intersecting tracks with deviating colours ;-)

But as I wrote earlier, I have only found this behavior in tracks made with an older HDS software version. The newest 2.5 version seems to be more stable. Another issue tha dissapered with the 2.5 was the dimming bug I had. Sometimes the HDS suddenly started to slowly dim itself down to black.


Matt,
One simple extra check during asset import could be to have a "Track import option" that excludes negative depths. I have got many of those in the bad logs.












The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2508

  • Matt
  • Matt's Avatar
  • Offline
Mats - there is no usable extra depth information in the sidescan channels.
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2509

  • Matt
  • Matt's Avatar
  • Offline
Interesting screen shots Mats - so the depths align with the 2D sonar OK at all times? Just to clarify, we only harvest depths from the primary channel, which for SL2 files is the lowest available channel in the recording. This will usually (almost always) be the primary 2D channel, but in the case where a recording only has DS and SS, we will take the DS depths. So, the depths you are seeing overlaid on the DS screen are from the 2D channel. From the colours of the track-points it is clear that the depths are not good in that track, but it is interesting that they seem to match the 2D OK.
I'd be interested to take a look at that data if you can share it? (upload to Google Drive or similar and send link to This email address is being protected from spambots. You need JavaScript enabled to view it. ).

Matt
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2510

  • Mats
  • Mats's Avatar
  • Offline
Matt, I have uploaded the file to my Dropbo account now. I will email the address to you.
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2511

  • dst
  • dst's Avatar
  • Offline
It might not be a bug in the HDS software, or at least not one that caused invalid/unusable logs.

Matt, I don't know if you've gotten a complete spec of the sl2 files from Lowrance or how completly you've decoded them yourself but if not have a look at the sounding headers for these files. At the start of the those headers there are some values linking together the primary, downscan and sidescan soundings. Looks like the primary is "stretched out", i.e containing fewer soundings in sequence than the others then it catches up with all the missing ones. But if you go by the index/offset/number values in the hearder instead of just reading one after the other that might fix it? But that's just a guess and I haven't really looked at the sl2 format since last summer.

Here's a snippet from my code in case that helps
    headerOffset = br.ReadInt32();
    groupedPrimaryOffset = br.ReadInt32();
    unknown0 = br.ReadInt32(); // Always 0?
    groupedDownscanOffset = br.ReadInt32();
    unknown1 = br.ReadInt32(); // Always 0?
    unknown2 = br.ReadInt32(); // Always 0?
    groupedSidescanOffset = br.ReadInt32(); 
    ushort soundingSize = br.ReadUInt16();
    previousSoundingSize = br.ReadUInt16();

There's also a running number for the soundings so for all I know they might be able to occur out of order (not that I've seen that in my few samples though)
Last Edit: 9 years 11 months ago by dst.
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2512

  • Matt
  • Matt's Avatar
  • Offline
They certainly look displaced in time, but the sonar viewer treats each channel entirely independently, and the position in the display is calculated from the time offset of each ping. Track-points are overlaid according to their time. The most interesting thing about these examples to me is not that the DS appears different to the 2D (although that might be part of the problem), it is the fact that the imported depths are clearly very wrong - as shown by the overlapping tracks in the point display at the left. Those depths in this example will all have been harvested from the 2D channel and relative timings/ping positions shouldn't matter, as both position and depth are taken from the same ping.. I'll need to take a look to try and understand what is going on - I can't rule out a problem with RM yet, but it's hard to see how at the moment.

Matt
The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2513

  • Matt
  • Matt's Avatar
  • Offline
Here is 2D over DS in the new viewer. This is the moment in the file where the depths start to diverge, and it seems that the DS is showing the correct depths. Time and position for the pings in the 2D channel appear to be wrong, and that seems to be a problem at the file level. I'll look into this further when I get the time but at the moment I don't think this is an RM issue, although it would be nice to understand exactly what is going on.

The administrator has disabled public write access.

Editing in Sonar viewer 9 years 11 months ago #2515

  • Mats
  • Mats's Avatar
  • Offline
I know this lake pretty well, so I can confirm that the DS depths are the correct ones.

I also doubt that there is a problem in RM, since the problem appears to have disappered when using later HDS versions.

Looks actually like a "real time" code issue to me. The code is not processed in time and no watchdog has stopped, so everything got delayed. This should of course not be possible in this type of code.


If anyone else (Lowrance?!) is interested in looking at the file, please find it at my Dropbox account below:

Sonar logfile
Last Edit: 9 years 11 months ago by Mats.
The administrator has disabled public write access.
SCROLL TO TOP