David,

Yup, those are probably for photogrammetry.

The "stitching" you mention all done digitally now. I've been at it long enough to have learned the old manual processes. We would "rectify" ( bring to scale and reduce tip and tilt effects) each image first.

It was important to make the enlargement on the lightest weight fiber paper possible. Even with rectified images features wouldn't necessarily match from one photo to another.

Once you had your prints, you'd soak them down and glue them onto masonite or some other stiff backing. The reason for the light weight paper was to allow you to manually stretch the paper to make things fit better. It was critical to keep the paper grain going in the same direction in all the prints ) to avoid differential stretch).

Anyway - more trivia - photogrammetry is used in Architecture as well. Stereo photos are taken of building facades and then they are mapped.

Later,
Terry