We need the orthomosaic of a small (~300x400 m) urban area (park, max. 10-15 m high buildings, streets, square).
We have made a vertical image acquisition (camera pointing to the nadir direction) of the area, grid flying at 60 m altitude with a DJI Phantom 4 - the result was about 350 pics. Overlapping of the images was as high as recommended by Pix4D. We used high precision GCPs (collected with RTK GNSS) for georeferencing.
The generated orthomosaic was odd, as some of the building facades (facing to the same direction) was viewable on that, although that should not, as the facades were perpendicular to the ground.
We have checked the densified point cloud - realized that these facades were also generated as not perpendicular to the ground. Checked the result and the report of the initial processing - realized that neither pics facing to the nadir direction according to the Pix4D, but all of these are tilted a bit (for some degree, all with the same amount), not parallel to the XY plane.
Do you have any idea why all the results are tilted and how to correct it?