Toilet bowls that only occur when using RTK

ArduCopter Copter 4.1
1

I have a drone with two GPS (Here3 and RTK) and when I use RTK I get a toilet bowl.

Oddly enough, when RTK is disabled and flown with Here3 only, the drone hovers stably, so I presume it is a GPS problem, not a compass problem.
The compass is provided by an external module, Here3.

Do I need to configure anything if I want to use RTK?

For parameters that might be relevant, I have the following settings
GPS_TYPE: 9 (Here3)
GPS_TYPE2: 5 (RTK)
GPS_AUTO_SWITCH: 4
GPS_PRIMARY: 1

Reducing PSC_POSXY_P and PSC_VELXY_D had no effect.
Each GPS_POS* parameter is set correctly.

The log can be found at the following link

For RTK
https://www.dropbox.com/s/aj8f0dc3y4l04pv/2021-12-07%2012-07-21.bin?dl=0

For GPS
https://www.dropbox.com/s/vbhg76pivrfs50b/2021-12-07%2012-18-12.bin?dl=0

Can you please help?

2

What do you mean by RTK as second gps?

3

It is equipped with a GNSS receiver that performs RTK processing. This receiver outputs the data in NMEA format and is set as GPS2.

4

So what I think is happening here is a misunderstanding of how fixed base v moving base works in Arducopter, but then again it could be my misuderstanding. In Arducopter the moving base is there to allow GPS to provide the yaw sensor, it does not allow genunie RTK even though RTK fixed may appear in the telemetery. If you want proper absolute RTK levels of accuracy then you will need a fixed base on the ground and not one on the aircraft. So in answer to your question I think you are getting a toilet bowl due to an incorrect setup of you GPSs.

If you are actually using the base GPS on the ground then again the setup is wrong as you need to connect the GPS via MP or equivelent and setup the base in the software with a live telem link to the aircraft to provide the corrections