Hello!

Currently considering using of high-precision GNSS receiver along with Lowrance HDS unit for preparing high accuracy depth maps.
So I see two configuration options:

1. Connect GNSS receiver to HDS via NMEA 0183 and prepare SL3 logs as usual
2. Connect both HDS and GNSS receiver to laptop via NMEA 0183 and use ReefMaster to collect Live data

Basically first option looks more feasible because I'll need less equipment in the boat but there is a question regarding synchronizing depth and position measurements in time.

If somebody had an experience with such a configuration what would you recommend?

Thank you!

The issue with option 1. is that the HDS will only record positions in the sonar log file with approx 1m (integer Mercator(ish)) resolution. You might find, however, that full resolution position is recorded in the trail files, which you can export with depth, so if you are only looking for depth and position information this approach might work, but it won't help much with sidescan mosaic.We have a solution coming for post-processing separately recorded position and sonar logs to synchronise them, which works around this problem - but it won't be available for a little while yet.

Hello Matt,

Thank you very much for your reply! This is so important to know that resolution for sonar logs cannot be better than ~1 m.This post-processingsynchronising will be perfect solution for described tasks - in this case there is no need to connect GNSS receiver to HDS or to laptop - that's great.

When you say that the trail file records depth and position at full resolution, do you mean at 10hz? If so this is interesting to me and I'd like to experiment with this. Do you know what the max point size is for a trail before it starts overwriting? I have never tried to export just a trail either. How does one do this with a HDS Live MFD?

After 2 years have returned to the question related to the usage of GNSS receiver along with Lowrance for precise depth records.
As Matt mentioned 2 years ago even if GNSS in RTK mode is used in SL3 file position is still inaccurate due to size of corresponding variable in the log file.
In the same time trails include precise position info but they don't include the depth for track points..

So the question is - is it possible to extract trail coordinates along with corresponding depths from the Lowrance unit at the same time? Or Live Track is the only way?

Hello Matt,

I Hope all is well. Your comment from a few years back "We have a solution coming for post-processing separately recorded position and sonar logs to synchronise them, which works around this problem - but it won't be available for a little while yet. "

This post-processing feature is something I require in the next month or so. I see from other posts the a possible RM 3 is still in the works, but in the meantime if there is any stand-alone utility or process that may accomplish this, i would be very appreciative.

Thanks!