We collect data with Lowrance HDS systems. The HDS has a built-in GPS, but it is not very precise. So we mount a Trimble GPS unit on top of the transducer which receives NMEA data about depth from the HDS and saves the depth in centimeter-precision depth according to RH2000 / BSCD2000 (Baltic Sea Chart Datum 2000). The Trimble data can be exported as a CSV with position in SWEREF99.

It would be quite useful to be able to import the Trimble CSV. First of all to get a comparison of the difference between positioning, which right now if I want to check that I have to do an export of Lowrance data and use R or similar software to get some graphs. Second of all to, in a best case scenario, connect the trimble data to sidescan so that all of the data we deliver can be said to follow BSCD2000 / SWEREF99 standards with RTK.

Usually the Lowrance GPS is within 0.5 meters of a correct position, so it's not a huge thing, but it would be nice to get all data completely accurate since we do have accurate positioning available.

This is something we have looked at and also done some work on. There didn't seem to be too much demand at the time, but it is something we can revisit. Our tests did show worthwhile improvements in sidescan mosaic, especially when used in conjunction with an accurate heading sensor (or headings are derived when using a pair of RTK units). It is worth noting that accurate headings are actually much more important than pin-point accurate locations when processing sidescan mosaics, and that headings can be recorded as part of the Lowrance sonar log already if the appropriate receiver is used.

Matt wrote: I did not know this, thanks for the tip!