Hi Pondguy,
Yes - it would be helpful to take a look at that file to see if we can understand what is going on.
If you could share it via Google Drive (or similar) and send a link through to This email address is being protected from spambots. You need JavaScript enabled to view it. that would be great. Note that if this is HB track we will need the .DAT file and the contents of the sub-folder with the same name, that contains the .SON files.

thanks,
Matt

Matt / pondguy,

Just a thought, and could be nothing to do with it, but might it be anything to do with the 'coastline' and 'Island' boundary? I noticed a lot of the extra grey points are very close to these (which I presume you used to get the background onto the map). Reason I ask is that I had a 'bleeding' issue around vector contours which went away after I turned the coastline off. Could it be that rm is taking the averages around the point, seeing that some are outside the coastline / island boundary and then nulling the point? You'll obviously know a lot more about the algorithms involved than I do matt, but is it worth trying to turn the coastline off and then trying to edit the points to see what happens (if you haven't tried that already).

That's a great thought Hermes.....but the screen shots I took above are from the sonar files so there is no way to put in the boundaries there. I have not tried that though and will.

Matt....access to the files via iDrive was just sent to you by email. Thanks for looking into this!

Thanks PondGuy, files received and I have managed to reproduce the issue, so hopefully we can get to the bottom of it.

I really appreciate it...thanks!

Thank you for the help all sorted

Matt,

Have you guys gotten anywhere with the bottom composition issue? I have noticed that more recently edited tracks (since update) are not doing that anymore.

Also one other quick question....

For the return strength on BC....is the lower limit of 10 referring to soft bottom and the upper limit of 200 referring to hard bottom? Does anyone know what return strength value might generally identify sand versus muck? We do a lot of work on ponds and are using the sonar along with RM to determine problem accumulation areas in stormwater ponds. The histogram for return strength is interesting and different for each mapped pond and I thought maybe there could be some good generalizations pulled from it. Any tips would be appreciated. Thanks!

Hi,
It turns out we were not allowing bottom-hardness information under a certain depth (1.5m) - the reason being that hardness values at these shallow depths less useful, as they typically overstate the hardness significantly. We have relaxed this restriction in the latest version, but I would still caution against setting too store by values in water this shallow. You might be able to mitigate this to some extent by truncating upper hardness values by using the Range option.

As for absolute hardness values - it is extremely difficult to assign meanings in this way. Hardness is a relative, "unitless" value, and the best you can realistically hope for is to gauge relative hardness/roughness. A large number of factors have a role in the actual values that you will measure, including your unit and transducer, of course, but even things like weather and water conditions will have an effect.

Matt

Matt wrote: Ah. Now I know why the 1m deep rockbar that I was fishing over wasn't producing a hardness map!

Hi everybody!

I have two more questions about BC which I've just purchased.

In the RM manual it says that sonar log files must be imported again after activation of the BC module. In my case BC seems to work without having to import slg files again? Is BC working correctly?

Also, I get significant differences when looking different layers (Peak SV, E1, E2 and composite). Which one should I look at the most? What do you suggest? For the E2 layer I will collect it differently in the future (according to your range instructions) since now I obviously don't have the data collected right from all the area I have mapped...:(

Riba wrote:
If you open a sonar log and check "Bottom composition" under the Edit-menu you will find histograms if the log has hardness data. If so no need to reimport. If blank histograms=reimport.
Riba wrote:
I use E1 since I have that data from most places and it works very good for me. But I suggest trial and error to find best settings for your hardware. If you know of some really hard areas on different depths, try to get RM to show that as well in the map. Smoothing and range settings are things to fiddle with.

If hardness is important I also suggest tuning the scale/offset (mainly scale) in the equipment settings if you mix data from different hardware.

/Martin

Thanks Martin!

What I can tell the E1 layer also looks good for me :), but I can't say it for sure... Also, I can't say if it would be better to mix the data (composite)? Is RM mixing the data from the E2 layer when it is not collected? That wouldn't be so good... If anyone else has some more experience I would appreciate it!
Also, when on the sea, what do you do, have more SD cards and switch them to see different layers on plotter? Or if you would like to see colored depth maps instead of bottom hardness maps at some point?