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Pix4D Mapper GCP & Picture

First I did an Initial Processing without GCP.s.  Afterwards I added my GCP’s.  Question Why are the BLUE markers lower then the GREEN markers?

Please let me know.  Thank you

Hi Kurt. The reason for this shift is that the initial camera positions (blue dots) are based on the camera geotags. These are notoriously unreliable in the Z axis especially. The green dots represent the optimized camera positions that have used the accurate geolocation data from the GCPs. This means that they have been more accurately placed in 3D space thanks to the GCP elevation information. This is not an issue and is a good sign that using GCPs has helped to accurately geolocate the project that otherwise would have been shifted vertically.