How to make landing more precise with DGPS?

ArduCopter Copter 4.0
1

I had DGPS constantly feeding in position to the mavproxy thru DGPS module at port 13320.

But it seems that the landing is still about 1metre difference. Is there a way to make landing more precise? I assume DGPS can reach centimeter grade precision, why the difference is in at least 1 mettre?

Anyone here tried precise landing using DGPS?

2

You need to tune the copter to get that level of precision. Did you tune the notch filters? used autotune?

3

Kindly enlighten me where can I find out more about this?

4

This forum is full of posts explaining it. Here once again for your convenience:

  • use “Alt-A” in mission planner
  • search for “arducopter dynamic notch filter”
  • search for “arducopter autotune”

Apply the steps in the presented order.

5

Ok will try autotune later.

I am using mavlink to inject the RTCM.

I now can achieve within 30cm landing without IR-lock.

Anyway in case anyone face the same issue. I realised

  • Using DGPS module in mavproxy, can achieve about 1-1.5metre accuracy when landing.
  • manually inject using mavlink and pymavlink. 30cm.

I think something to do with the RTCM. The position in mission planner kept moving around.

I don’t seems to be able to achieve RTK using mavlink without using mission planner. Still trying to figure out how. Only able to get 3D DGPS.

Also I realised if I turn to manual control example poshold or alti hold, there is a lag between injecting rtcm and injected manual control command making it impossible to control safely. I think its necessarily to turn off the rtcm update when doing manual control.

It works great with auto mode though.