I just recently joined this forum, and noticed this thread.
I don't know if there is really any interest in it, but:
I've been in photogrammetry ( topographic mapping using aerial photos) for
over 25 years ( oh man, that's a long freakin' time...).
The pirmary use for the aerials that inthedark describes was for this purpose. They are generally shot in stereo ( 60%) forward ( along the flight line) overlap. We use the hard copy photos in whats called an analytical stereoplotter and scans of the negs in whats called a softcopy stereoplotter.
Lots of geometery and other stuff, but the idea is that we look at one photo with one eye and its overlapped mate with the other - stereo viewing. By working with a land surveyor ( who puts out crosses - either painted or plastic) in the scene to be mapped. He then gives us coordinates ( x,y,z) of these targets. We can then relate the photos to each other and the ground coordinate system. They are then measurable.
We have archive photos of our area going back 30 years. There is a market for them, but it is not terribly active hereabouts.
So, there's a lot of trivia for your distraction.
Hope it helps rather than confuses.
Oh, yeah, the other varialbe in the lab is that we use 10x10 Saltzman enlargers. They can tip and tilt the negative to re-create the attitude of the
aircraft at the time of exposure. This corrects for perspective displacement from that tip & tilt.