Better for them to send you the track files (.HT) - which they will be recording anyway. If you tell these people to periodically save & clear the current track, then do an Export all Nav data at the end of the day, they will get a set of .HT files containing position and depth. These are relatively small and can be imported into RM or converted to GPX using HBPC. It is possible to record sonar at the same time, if they still wish to log their trips.
There are some issues with the "current" track log in HB units if the track is allowed to loop past the 21K track-point limit. The track seems to lose depth for all points within the track, so the track should be saved before that point, and then the current track cleared. There are 50 slots for saved tracks.
It is also a good idea to change the track-point recording frequency to the minimum (1s) as this produces more data. If you need varying water level offsets (tide) across a track, then you also need to know what this increment is when importing into RM.
