I have a time series of UAV flight acquisitions (one flight per day for five days) from the Greenland Ice Sheet. This environment has a couple of key challenges:
1. The ice moves/flows at 0.5-1 m a day, so any GCPs laid out for the time series will be in a different geographic position at the end compared to at the start.
2. The ice melts, so GCPs laid on the surface will gradually lose elevation.
For point (1), my way around this (because I'm interested in comparing the same point on the ground at each time, even though it has moved in geographic space) is to leave the GCPs out for the entire time series, surveying them just once and using these same coordinates for all the flights - effectively cancelling out the ice motion.
However, point (2) is where I run into difficulties. Ideally I would let PhotoScan ignore the Z-coordinate of the GCPs because the Z-coordinate is only correct for a single time point and not the entire time series. I instead want Photoscan to estimate Z by itself, but still using my essentially fake X,Y coordinates.
In other words - is it possible to disable GCP matching in the Z dimension?
(Note - there is no stable ground in these acquisitions on which to distribute GCPs - the nearest land is 30 km away!)