Hi all.

After succesfully using for almost 2 years a Phantom 4 Pro for Surveying / Mapping purposes, I've decided to purchase a Phantom 4 RTK;
- Obviously, like so many others in here and in other relevant forums, even though I eventually found out a workflow to incorporate my country's geoid and coordinates, I am still having that 20cm difference in Elevations (Ortho Heights). I have managed to extract automatically all the exif data of the photos in a csv file, hoping that I will be able to substract that 19.2cm value I've been reading and then test some more but it's only to be found in the corresponding MRK file. The $1000000 question; Has anyone figured it out?

- My second problem has to do with the camera settings; Apart from not being able to acquire the photos in raw format I can' t seem to find a way to manually input the camera settings I want eg steady ISO, Shutter Speed & F-stop. Once the bird is in the air, my settings are forgotten and camera is set to auto. These settings are critical for sharp photos and many matches in the alignment procedure.

I must point out that I have the latest settings in both controller and drone (2.01 excluded).

Thanks.

We are seeing the same error.  I thought it might be an antenna phase offset misapplication within the code, but the error is slightly different (+/-150mm) across all of our RTK units.

We are in the process of looking into the possibility that it is an issue with  the camera calibration settings that the photogrammetry software generates (Agisoft).  We are going to generate a custom camera calib file for one of our units today and see if it makes any difference.

We are still relying on 2 x GCPs in the flight capture to allow us to do a block shift of the elevation difference.  As the X/Y is so accurate, it does not seem to have much of a detrimental impact on the model quality, however, I wouldn't use this method to adjust anything over 400mm.  

If anyone has found a method that works, love to hear about it.

Cheers

I’ve had this same issue. I’m pretty sure there is something weird going on with the camera calibration as calculated by Agisoft, however I’m not certain. Try taking some oblique photos. Include these photos for the initial alignment and any optimisations, then disable before creating the dense cloud. This seems to greatly increase the accuracy of my reconstructions.

Thank you, will get some oblique photos as well. This will definitely increase the flight time though (there are flight needs for surveying purposes, almost everyday)..
I have read that with 2-3 GCPs absolute accuracy increases dramatically and it seems logical.
May I ask everyone in here about calibration settings of the camera? So far I have tried precalibrated settings from DJIs' file - with distortion correction off, of course- and I had a vertical offset of +20cm this time; the previous flight was with distortion correction and the check points from the point cloud created were actually 20cm lower (on average) from the GNSS RTK measurements.
What about the ISO/F-stop/Shutter speed that keep changing during flight when I told them nit to, is there any experience?
Thanks!!

DJI4Survey Posted at 5-12 14:12
We are seeing the same error.  I thought it might be an antenna phase offset misapplication within the code, but the error is slightly different (+/-150mm) across all of our RTK units.

We are in the process of looking into the possibility that it is an issue with  the camera calibration settings that the photogrammetry software generates (Agisoft).  We are going to generate a custom camera calib file for one of our units today and see if it makes any difference.

@DJI4Survey
I put Phantom 4 RT on the ground, made photo and then I checked this spot level with Leica RTK GPS. By my check this is Phantom GPS antenna error in EXIF data. However it will be changing during the flight depending on camera position and drone angle flying against the wind. DJI should recalculate antenna offset above camera for each photo and apply value to it.