- B000, secondary, usually 83khz.
- B001, primary, usually 200khz. Depths for mapping are taken from here.
- B002/3, sidescan channels port/starboard. Depths are taken from here for slant-range correction only.
- B004, down-scan.
It is not possible to select a channel for use in mapping in RM, although we are considering adding that option in the future.
If you *really* want to try a different channel, you can try renaming the .SON file. E.g. rename B000 to B001 before you import the file to RM. RM would then just treat this file as if it were the primary, although you will get some odd effects in the sonar viewer and bottom hardness calculations if you use a sidescan channel as primary.
If you do start changing sonar file names, I would strongly advise taking a backup of the directory first!