Paul,
So I guess you’re talking about a setup where the flight controller (i.e. Pixhawk running AP) or ground station (i.e. Mission Planner) is providing a position to an external piece of software that’s then combining that position with the sonar data. I can’t really help with this… like I mentioned above, I’m hoping to extend APSync (running on an RPi3 or NVidia TX2) to be able to consume the “back scatter” data from the sonar and combine it with the vehicle’s position received from the flight controller… and for the moment, AP can record position and simple depth which can be relatively easily uploaded to ReefMaster as shown in this blog… but that’s as far as I’ve gotten I’m afraid.
… I see that on the MP’s Ctrl-F screen it’s got a “NMEA” button that outputs nmea messages… but I’ve never used it so I can’t really provide any advice on how that might work.