DUAL RTK heading question (true or mag needed?)

ArduRover Rover 4.2
1

I have a North Dual RTK receiver that gives me fixed RTK positioning + NMEA HDG sentence with true heading based on the dual RTK antennas. Works good but my question is what does Rover 4.2.2 expect ? Does it expect true heading to compute the track required between waypoints so must I calculate and provide magnetic ? Or pass true via the HDG sentence ?

The final configuration of this project is a tracked vineyard robot (35 hp, 1500lb). I have been working on it off and on for 5 years (more off than on!) and it keeps getting more functional.

Thanks in advance.

2

what RTK GPS receivers are you using?

3

I use DualRTKite from North Surveying in Spain. It has 2 antenna feeds and usse a North ground station with UHF radio link to get RTK corrections at 20Hz. It does the trig math and outputs the true heading of the rover in NMEA HDG sentence. I tried it sending either mag or true and I think that the waypoint track is computed relative to true North so true north appears to be the needed heading.

4

I believe they use UBX-NAV-PVT for heading when you’re using Ublox units - I haven’t checked if ArduPilot accepts the NMEA equivalent.

5

ardupilot handles NMEA. The whole setup works quite well. maybe 10 cm drift. The next thing is to improve Rover tuning. I can get it to follow a path but still working on getting all the tuning params right so I don’t get jitter and better xtrack accuracy. Any tips from anyone appreciated as the documentation is a little sparse.
BTW: I think the skid-steer mapping in ardupilot is not great. I have implemented my own, and am testing it side-by-side.