I am afraid you won't be able to use RTK without at least 4 GCPs. There seems to be some issue in CC that it doesn't correctly handle alittudes(7000882953) and I have not still got answer from Bentley regarding this issue. I noticed constant 5-7m difference even with accurate altitudes. At first try to do a calibration if you process only Nadir flights. Also make sure that you use unprocessed(distorted) images and not undistorted but actually could try with undistorted also. Undistorted images from RTK are already flattened using factory calibration( DewarpData) so could try to reuse the calibration. https://communities.bentley.com/products/3d_imaging_and_point_cloud_software/f/contextcapture-descartes-pointools-forum/176371/dji-phantom-4-rtk-ntrip-processing/510761#510761 So basically what is needed for RTK processing: 1. Create local coordinate system with your locally used geoid which was used for GCPs. 2. Import images and set "GPS Altitude reference" to WGS84. At least for me it seems that DJI for RTK uses WGS84 for GPS altitudes whereas in non-RTK products the GPS altitude tag contains barometric altitude. 3. Reuse precalibration parameters. Other method if launch altitude is known we could do aerotriangulation 2x times, first to get the wrong altitudes then adjust the altitudes by known difference and run aerotriangulation again.
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