Can someone please give me some guidance configuring a RTK GPS with a normal GPS as backup. I am experimenting with a low-cost Quectel LC290HEA 10Hz RTK as a Rover. It is connected to a Pixhawk 6C on GPS2 and receives RTCM messages via Mavlink2 from a ‘relative’ base station (LC290HDA 1Hz) and normally easily holds a reliable RTK Fixed status. When flying my Hexacopter with just the RTK GPS configured as the sole GPS source I achieve relatively stable flight and RTLs within 0.25m.
However, when I configure a second non RTK GPS to act as a backup, the drone becomes uncontrollable drifting many meters in all directions while in Position mode, and results almost always in a crash. I have tried configuring numerous parameters and it makes no difference. ( EKF2_GPS_CTRL, EKF2_GPS_CHECK, EKF2_GPS_MODE, EKF2_GPS_P NOISE, EKF2_GPS_V-NOISE, SENS_GPS_MASK) .
I have a feeling I am perhaps missing something fundamental. I attach a flight log as an extreme example when after take-off the drone flew-away (800m) totally uncontrollable and miraculously did a RTL with precision landing ! (This was the only time I got the mysterious warning ‘RTCM output have to be configured manually’ … if the RTK GPS had lost RTCM updates I should not have lost control)
https://review.px4.io/plot_app?log=b29b77c1-05b3-4fd0-94c5-a4dee1352c0c