Also,

Last time I was on the water I accidentally did not record all the channels so I made .slg files instead of .sl2 :( Besides last question, I have also noticed that when I made a map using .slg files only, I got better results using E1 layer than E2 (which I had recorded all the time)? Can it be that when having .slg files the results are better with E1 layer and when having .sl2 the BC map is better with E2 layer (supposing you have one all the time)?

Does anybody know anything about these last questions of mine?

Matt, please...?

Hi Riba,
There really shouldn't be a difference between the two, assuming that you were recording the primary (200khz) channel in your slg file. The primary channel is always used from sl2 files, and mixing logs with different channels is not going to give you good results.
What channel were you logging to your slg file?

Hi Matt!

Thank you for your answer:)
Yes I was recording the primary (200kHz) channel in this slg file. As I said, these tracks recorded in .slg format show harder bottom composition than the ones recorded as .sl2. What should I do? I would really like to use these files also!
I have attached the picture.

Matt, any ideas on this?

Do you want me to send you recorded files?

Hi Riba,
Mixing source data for bottom composition does not produce good results, so I would suggest sticking to either sl2 or slg files when producing your hardness maps. You could try adjusting the scale and/or offset of your slg track to see if you can bring it into line with the sl2 file, but there is no guarantee that this will work.

Matt

I am sorry to hear that:( but thanks for the answer:) Now I know what files I can use and how to record in the future. That's still something and BC is still a very useful tool:)

However, is there a chance that this issue might be solved in the future versions of RM?

Riba wrote:
Missed this question. This is normal behavior for some strange reason. Always record in sl2 as this (according to DrDepth author) provides better data for hardness.

But - you can mix slg and sl2 (or data from several sources) in one single project. It involves setting up different equipment profiles in RM. One for SLG and one for SL2. And in the equipment profiles you tune the "scale" and "offset" values so that the end result hardness values are harmonised. This can take quite a bit of work. At work now, I can post my settings for slg and sl2 later when I get home. But these are for HDS gen 1 with Airmar P66 transducer - your hardware might require other settings.

/Martin

SL2 has scale 1.0 and offset 0, meaning it is my "base equipment".

SLG has scale 0.5 and offset. So I half the hardness values from slg-files compared to sl2, pretty big difference!

I have found this to work by sampling lots of data and comparing histograms from the different file types.

To make it even more interesting older firmwares of the same hardware has other values but that is probably very specific to the Airmar P66-transducer.

Hi Martin!
Thank you for the answer! I have set the forum option to follow all topics but somehow I didn't get the message that you answered this question of mine that is the most interesting to me at this point:-( Never mind, I am really glad that there is a solution to this problem. In the meantime I was also trying to solve the problem by setting scale and offset but didn't get any results. Now I know why. I was setting different parameters once the tracks were already imported and there was no change on the map. So, as you say, the parameters must be set already at the import stage! Thanks for this information, you saved me a lots of time searching for the problem:-) Also, I have noticed that the sl2 tracks recorded by a friend of mine (having different hardware) show even softer bottom than my sl2 tracks. I suppose I will have to solve this problem the same way. Thank you for the settings too! I also have HDS gen1 and Airmar transducer so your settings might work! Last couple of weeks I was busy getting my boat ready for the season so I didn't have much time to explore all RM BC options but I can hardly wait to get to work on new maps. Thanks again, I really hope that this is going to work for my recorded files!

Hi Martin and all other interested!
I was trying a bit more to set scale and offset and I managed to do this without having to do it at the import stage. Before, I was getting no results because I was setting to small scale difference! When I set scale at 0.5, there is a difference! However, I still think the results are not perfect. How about the offset, Martin do you change offset for slg files? To me it looks better when I set the offset at -2 or -3 for slg file?
In the RM Manual it says that the signal Histograms can be useful when adjusting these parameters. How can I use them?