EKF2 position estimates are way too off compared to precise RTK GPS location[Bug]

[slgrobotics]

Describe the bug

I have a dual RTK GPS setup on a rover (lawnmower) - delivering centimeter accuracy Lat/Lon/Alt and heading with sub-degree precision. This data is, naturally, fused by EKF2 and its estimates are published as VehicleLocalPosition and VehicleGlobalPostion messages. I started logging the discrepancy between the Global and RTK GPS data, and here is the typical result: While the 0.3 meter deviation and oscillations may be acceptable for a drone in the sky, it completely messes up any ground base vehicle trying to stick to its course.

My solution to this problem was to override Lon/Lat x/y and heading values immediately after receiving the *Position messages, and that works well.

I still would consider delivering imprecise estimated values when accurate location data is available to be a bug/oversight.

It would be prudent to pass through unmolested RTK GPS data in these fields when GPS fix_type==6

To Reproduce

Have an RTK GPS equipped rover or drone and log discrepancy between actual coordinates and EKF2 estimates

Expected behavior

EKF2 should fully use accurate RTK GPS data and not substitute it with imprecise estimates

Screenshot / Media

No response

Flight Log

https://review.px4.io/plot_app?log=6be08335-a60f-468b-93cb-f16291ef5688

Software Version

Current main

Flight controller

Raspberry Pi 4

Vehicle type

Rover

How are the different components wired up (including port information)

No response

Additional context

No response