Hi Riba,
You can't mix layers in a single map - the results wouldn't be useful in any case. E1 is usually the best bet, unless you have good E2 coverage, which most people don't unless they are collecting specifically for bottom composition.
You shouldn't need to reimport anything now, as BC data is always calculated regardless of whether the module is installed. The reason for the warning when we first released BC was that this import was not present in earlier versions (pre 1.6), so at that time a re-import was necessary.

Matt

About visualizing hardness in the map that is done with different "layers" or polygons. I don't use the standard RM settings for this so I don't know what they are, but they should be useful right out of the box.

I use a transparent darker shade for hardness (the harder the darker shade) on HDS-units and grid-icons to show it on LMS-units (that cannot do transparency). I think info about this already exists on the forum

Thanks Matt and Martin!

When I was writing about "mixing" data, I meant the possibility of using the Composite layer... So, as I understood you correctly, it is your opinion that it is better to use E1 than Composite if I don't have good E2 coverage. (Of course that I will check it out on the sea :) but I am trying to collect some experience before spending hours on the sea...)

If the E2 layer is shown on the map (for some area), does this mean that the good E2 data is collected for that area?

I have tried to use opacity feature for the BC layer when creating maps but the result is not that good for my purpose. I have used many colors when I created depth maps and when I use a BC layer together with depth map, there are too many colors and I cannot see either well.
So what do you do on the sea, have more SD cards and switch them to see different BC layers on HDS? Or if you would like to see colored depth maps instead of bottom hardness maps at some point?

Hi Riba,
Try using a monochrome palette for bottom composition - this overlays colours without causing a colour clash, and is what I typically do.
You can turn chart categories on and off whilst on the water - pull up the chart categories menu on your unit and select/de-select bottom composition. Likewise with depth areas.

Matt

Hi Matt!
Thank you for the advice! I will definitely try it.
Do you have any suggestions about first two questions?

Hi everbody!
I have tried BC with the new data collected especially for BC (deeper range, have E2 layer all the time) and I am very pleased with the results. However, I still have some questions.
I saved two tracks of the area. The first one 50 kHz and cone angle 45 degrees and the second one 200 kHz and cone angle 12 degrees. With 200 kHz I got good results (best with E2 layer and a bit worse with E1) but with 50 kHz the results are not good:( When I created a map using both tracks the results were not good. The map was showing the harder area wherever is data collected with 50 kHz. Is there a way I can mix the data collected with 50 and 200 kHz? What is the case with ordinary depth maps? Up to now I have always created maps out of 200 kHz sonar logs only. What does RM do if I have both channels logged at the same track?

Make sure to always record 200kHz and only use that. That should give the best result.

If you have a Lowrance you can record all freq in one single "sl2"-file incase you need 50kHz for other purposes.

Thanks Martin!

Actually I don't need 50 kHz for any other purposes but I use it because it has 45 degrees cone angle and that way I "see" the larger bottom area when searching for fishing spots.

Anyhow, this E2 layer seems the best to me and I do have it recorded in many tracks when I kept the sonar range on "auto". However, for some periods of time there are no E2 layer recordings. Does RM interpret this as "no E2 layer reading" or "very soft bottom"? If it interprets it as "very soft bottom" than E2 layer is good only if it was recorded all the time and if RM can recognize that there is no E2 layer reading because the range was to small, then I could still have very usable E2 layer maps from my old tracks and combine them with the new ones:)
Which one is the truth?

If there isn't enough range for E2, then RM won't use anything (assuming the E2 layer is selected), so you'll get an empty area. "Composite" uses an average of normalised values from all three layers, and can work with as few as one layer, but for best results I would recommend sticking to a single layer, preferably E2.

Thanks Matt!

Nice to hear that my old recordings contain valuable E2 layer data and that, in the future when I collect some more E2 layer data, I can use it together to get the best results :)

So you believe also, as Martin says, that it is the best to stick to 200 kHz frequency or there might be some way to work around it?

Hi Matt!

Any opinion on this last question?

Hi everybody!

Here I have one more question. I have noticed that the tracks recorded in .slg format show harder bottom composition than the ones recorded as .sl2. Does this mean I can't mix .slg and .sl2 files on one map? Is there a way to work this out?