P4P crabbing during mapping missions

[Bigriver]

My P4P is crabbing during mapping missions. Initially I thought it was the Litchi app, however I tested MapPilot and Drone Deploy with the same results. The aircraft flies the correct path, but the photographs are yawed. I use Pix4D for processing and the data shows the initial position (blue in attached image) of the images properly aligned, however the computed positions (green in attached image) show that the images are canted several degrees. The images are also visibly rotated. I believe the mapping results I am getting from Pix4D are accurate, but since the images are not aligned properly, overlap settings are mostly meaningless.

I was wondering if any of you have experienced similar issues? Any thoughts on settings that I should check? Or should I disregard it and continue mapping as usual? I have re-calibrated the IMU, compass, gimball, and controller.

 

[N017RW]

While having no experience with mapping or Litchi, etc... IF I understand your issue correctly crabbing can not be avoided to maintain a desired course. Aircraft always has to compensate for wind or air currents like boats do for water currents.

 

[sar104]

You need to take a look at the flight logs to see what is happening - i.e. is the aircraft heading incorrect, or is it just the gimbal. If it's the heading (yaw) then that suggests a compass issue.

 

[sar104]

While having no experience with mapping or Litchi, etc... IF I understand your issue correctly crabbing can not be avoided to maintain a desired course. Aircraft always has to compensate for wind or air currents like boats do for water currents.

Since it's a quad and thus can fly in any direction, it does not need to crab to correct for crosswind, it should just apply appropriate roll.

 

[N017RW]

Since it's a quad and thus can fly in any direction, it does not need to crab to correct for crosswind, it should just apply appropriate roll.

Yea. That crossed my mind after posting.
Thanks

 

[Bigriver]

I appreciate the input. It took some time, but I was able to download and analyze my flight data file for the first time. There is a LOT of information in there.

I picked a time that the nadir image appeared yawed about 15 degrees. Using adjacent location readings, I computed that the a/c was moving at an azimuth of 328 degrees. The "compass heading" registered 326 degrees, and the "gimbal heading" also registered 326 degrees. That seems well within reason.

So why are the images skewed? Should I check any other readings? I'll keep testing and report any findings, but I appreciate any suggestions in the meantime.

 

[doktorinjh]

So why are the images skewed? Should I check any other readings? I'll keep testing and report any findings, but I appreciate any suggestions in the meantime.

The aircraft is going to fly between waypoints using it's GPS position, which is independent of compass. If the compass is off, say 15 degrees, then the aircraft will fly skewed 15 degrees, but still fly in a straight line because it's navigating by GPS. If you can see that the drone is crabbing, Pix4D is telling you that it's crabbed, and the photos show it crabbed to the direction, then I'd try to recalibrate the compass in an area free of any metal. Be aware that reinforced concrete slabs and other unseen utilities can have metal that will mess with your compass before take-off/calibrate.

 

[Bigriver]

A lot of times I am very near the truck when I launch the drone, which could cause compass interference. And when it is breezy, I have been known to fire up the motors in the truck and hand launch. I will pay closer attention to this on future flights and see if it helps. Many thanks for the input!

 

[heliozinhow]

I have the same problem here.

Just to confirm: Is your Y error in the report too high? (Geolocation Error Y [%])

Regards,

 

[Bigriver]

The Y Geolocation Error does not seem excessively high. Attached is a screenshot from the report.

 

[Vman@rekon]

Bigriver,

Have you found a resolution to your issue? I own mulltiple types of DJI drones from the Mavic Pro up to the M210 and M600 Pro and they all exihbit this behavoiur save the M210 when you are using RTK mode.

 

[Bigriver]

No, but it does not seem to be negatively affecting my results, so I am just learning to live with it. The crabbing seems worse at times, but I have not figured out why.

 

[kitefiter]

I have a lot of experiences where the photos are skewed. They appear to make no difference in the results as the processing is just looking at pixels. As long as I have sufficient overlap, everything has turned out good.

 

[chascoadmin]

I know this is an old thread, but as of about 6 months ago we started experiencing a 15° crabbing with all of our Phantom 4 Pro's. V1's and V2's. Is anyone aware of any firmware issues? We map primarily with DroneDeploy so I am currently working with their engineers, but there's no way to confirm which side of the coin the problem lies.