Thanks for your thoughtful response… please see my response below.
Re-calibrating your compass as @MadRC described might be just what you need and that may resolve the issue. Try that first since it is little to no cost.
I have gone over that page linked… there is not much to do but set it up correctly and I have done so… this exact design has been done before, using all three compasss (yes only one is used for nav) no issues no need for compass MOT etc as the compass is far from electrical interference.
Otherwise, we need to isolate is which device is ‘correct’. Unfortunately, your experimental design outlined here does not accomplish that. If the two paths matched precisely, we could assume that each path verified the other. However, due to the fact that the two paths do not match, we can assume that one is correct and the other is deviating from actual.
How and Why do you trust your standalone GPS device?
the stand along GPS device is a post processed corrected position. 100% accurate as we use that to verify our point cloud data and camera stations are all well within spec. So we know that the secondary GPS is correct, that much I can guarantee.
What if it is the incorrect one and the Here2 is actually correct?
See above.
You would need to test a third GPS device in order to isolate the issue here.
Do you have a third, different GPS tracking device you could try? The results could verify either the Here2 or your standalone as “correct”.
See above
Assuming your measured path is correct - some deviation from the planned route is to be expected. How much is tolerable is the question. What is the scale of your mapping area?
Deviation is acceptable but this is pretty bad. Also we have never seen this behavior before, we have been flying our payload and survey missions for years. You can also see that the behavior is repeating row after row. I have a feeling some sort of IMU filtering was sacrificed when the IMU switching issue was resolved. The IMU is used in navigation for positional estimation and I think it’s estimating position wrong.
Is your track of what the Here2 “thinks” actually the recorded KML/KMZ? or is that your planned route from your GCS?
That track is the Here2 exported KMZ recorded onboard the drone, then clamped to grade in google earth.
What is the max deviation between planned vs measured? If that is within the stated horizontal positional accuracy of ±2.5m (±2.0m w/ SBAS) [datasheet here Section 1.3, Page 6: https://www.u-blox.com/sites/default/files/NEO-M8_DataSheet_(UBX-13003366).pdf] , then you might need to look into RTK solutions in order to achieve a higher measurement precision.
difference between planned and measured by here2 is very little… it thinks that it is flying correctly. However post processed positional data is way off (again never seen this before).
Yes I understand that post processed can be a few meters off. However we have never seen this before and as you can see it’s a regular pattern. If it was just the difference between post process and non post processd data then it would deviate somewhat equally around the path.
finally I also created a non post processed path from the survey payload which showed the same deviated path.
I think that the Pix thinks it’s on course however it is not. Hence why the planned path matches the Pix hawk logs. The pix hawk is not trying to correct course because the pix thinks its on course.
So that being said there is no point in adjusting any variable to make it follow the course more aggressively. The drone thinks it’s doing a good job.
Finally we have done some 1.2km strips now and the arced paths are still there but the arc just becomes longer so it is less noticeable.
Any other thoughts appreciated.