I am new to PPK processing and would like to get a second opinion on my PPK results and workflow.
We flew a small area of 1sqkm to test our Powered Lift aircraft fitted with a modified Sony 5100 (Foxtech Map01 with 16mm Sony lens).
Before flying, we marked out 7 GCPs in the area with a Leica GS18 GPS unit.
We used RedCatch to process the aerial imagery and apply corrected geotags (in WGS84) from the Base and Rover logs.
We processed Step 1 of this imagery (image input WGS84 and output GDA94 / MGA zone 56) in Pix4D, ensuring camera optimization and matching was all good.
We imported GCPs (logged in GDA94 / MGA zone 56), changing all horizontal and vertical accuracies from 0.02 to 0.05 and marked 3x as 3D GCPs and 4x as Check Points, and Reoptimized.
Quality report showed excellent accuracy as shown under “Ground Control Points” section. Link to report here: https://www.dropbox.com/s/j85xb64707pfxp3/REDToolbox_Pix4D_Project_report.pdf?dl=0
To verify this, we ran Step 2 and 3 and used the Point Cloud to generate a surface model in different software. We re-marked GCPs on this surface model - including some extra independent check points not used in the pix4d processing and measured the points in the model. Again, RMSE showed just 19mm error in X, 13mm in Y and 30mm in Z - similar to the accuracies in the Quality Report (and within our target range of 50mm).
We are concerned these results are too good to be true!! What we would like some reassurance on is:
- Does this workflow look correct for PPK processing?
- Are there any other measures of accuracy we could perform to prove the level of accuracy?
- Are we looking at the right metrics to judge the accuracy?
Perhaps this level of accuracy can be expected (and trusted) when using dual channel GNSS/survey-grade equipment?!