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ROV plotting on nautical chart, and ship + ROV on same chartplotting

(Bo Koppel) #1

I have finally found a way to use nautical charts for plotting ROV position.
Thanks to OpenCPN Håkan!
Ship is showed on same chart, so moving ship after ROV is now easier.
Same info can be sent to plotter at helm.
Info like distance to ROV is possible
-OpenCPN software with charts.
-Underwater GPS to have position of ROV into PC.
-Basic GPS (and headíng sensor) to position ship as usual, via serial port or UDP etc
Trick to get ROV position is to use NMEA string $RATLL via UDP for sending ROV position to OpenCPN. OpenCPN then thinks You are plotting a radar MARPA taget and displays that.
String is sent from Waterlinkeds modified Python NMEAOutput module and looks like this:
Where 01 is ship ID, lat, long, Shipname(ROV), GPS time, T is tracked, *75 is NMEA checksum

Below is testing via Waterlinkeds demoserver

(undersearobotics.com) #2

Very clever! You might also be able to use this same method if the ROV has an onboard GPS. How did you manage to get the system to translate the NMEA sentence to $RATLL?

(Bo Koppel) #3

I used Waterlinked Python examples from their website.
“NMEAoutput” and modified that from standard GGA output to TLL sentences.

I put module to Github, I’m new on Github, this might work:


Very cool Bo! Thanks for sharing!