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Author Topic: Historic Aerial Alignment  (Read 490 times)

wgreenePIMS

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Historic Aerial Alignment
« on: November 17, 2021, 07:57:42 PM »
I'm having an interesting issue with the alignment of historic aerial imagery in Metashape 1.7.3. I have a set of 69 scanned photos for which I have the focal length and film size/scan resolution. Most of the scans include all the fiducial marks, but some of them have one of the marks (on the top) cropped just out of frame. They are all sized the same in terms of pixel dimensions, so Metashape automatically recognizes them as a single calibration group. If I do not check the box for film camera with fiducials, Metashape is able to align all the photos without any issue, as there is plenty of overlap to work with. This method introduces some significant errors, however, because while the scans are the same dimensions, they're not all aligned perfectly to the fiducials, and thus the camera calibration is not super accurate. When I try checking the box for film camera with fiducials, and then calibrating fiducials, it does a good job of predicting the location of the fiducials that aren't set manually, even if the 4th one appears out of frame. At that point in the process, it seems like Metashape is doing it's job well. When I try to run a camera alignment after doing all the fiducial work, it cannot successfully align the set. Sometimes I get up to 34 cameras aligned, and the program seems to do a good job with the calibration, but I am unable to get the rest of the set to align. I'm not sure how to proceed because the project requires a high degree of accuracy (~1m or so), so any help would be much welcome. I guess a part of the question is whether Metashape is able to deal with historic imagery where in some cases, one of the fiducials is out of frame. Thanks!

Will