[scottshambaugh]

I'd be very interested in the systems advertising that! I have not seen that even for stationary surveying equipment. I think it's also important to distinguish between RMS error which is often the better topline spec that companies give you, vs the 95% confidence error which is the more relevant one for flight reliability.

[michaelt]

In the specific case of a docking-type manoeuvre presumably you only need the highest accuracy when you're getting very close to the target.

No reason you couldn't use RTK GPS for <10cm accuracy for most of the flight, then in the last few meters of landing switch over to to high-precision, short-range tracking - like optically tracking a marker on the grabbing arm.

For other specific cases - like bridge monitoring - there are reports of 2–3 mm precision [1]. Of course, bridge monitoring has quite distinctive requirements; a 5Hz vibration component and a 0.0001 Hz thermal expansion component. So there's a lot of potential to average over lots of readings to reduce noise.

[1] https://www.sciencedirect.com/science/article/abs/pii/S02632...

[londons_explore]

If you want to land 99.9% of the time, it really is te 99.9% circle you should be looking at...

Or in fact, you need even better than that, since you don't want your whole error budget used up by the GNSS system.