HIstorical aerial photos - general processing and photo alignment

[danielf]

Hello everyone, I am new to the Photoscan-Metashape world.

I am just starting to use this package using historical aerial photos (digitalized from original negatives). I have knowledge about photogrammetry from using other software but am stucked at photo alignment here, and was hoping someone could help me.

For camera calibration, I have the focal length and fiducial coordinates. I do not have the pixel size in mm though. Marking of fiducial marks seems ok. Considering the origin of the coordinate system at the photo center, X axis to the right and Y axis downwards and after placing the first two fiducial marks, the third and fourth fiducials appear automatically at the right place, so I assume internal orientation is OK.

For coordinate system reference, I have created a GCP text file which is correctly uploaded., and I have placed the markers (GCPs) on each photo (between 4-8 on each one).
This way I assume this is sufficient to perform photo alignment, but I get the same error message of "bad allocation" everytime I try to align photos.

What am I missig here? Could  be the missing pixel size? And if so, how can I calculate it in mm?

Many thanks,
Daniel