Real Stereo Models, Proper 3D: How Experts Like Me Use Airphotos
First off, I locate what dated airphotos exist either in government or commercial libraries and advise you which of these would be most useful for your case.
Proper 3D is not like Google 2D airphotos (which are flat). They also differ from the fly through 3D simulations that they offer. Since WW2 vertical airphotos have been flown in lines across the countryside sometimes across a particular county. The plane progresses and it takes photos at a precise timed interval: in this way every house and garden, every bit of the landscape is covered by two photos.
Using two overlapping photos and the mirror stereoscope shown on this website, I can see slopes and hollows, the height of houses, fences, trees, wheel ruts or mounds of earth and distinguish the difference for example between a rectangular sheet of plastic on the ground and a shed of the same size and colour. Simple! People or vehicles in movement across a site appear in different places on adjoining photos. It’s a lot of fun! Shadows help identify things. For shed also read car, van stored object, pile of sand etc.
I add into this my detective work based on long years of expertise in identifying land use, footpaths, trees, crops, disposal sites and particular signs of wear. And of course how people do things on land they control.
My photographic 3D model can be enlarged optically or viewed on screen or as 3D photo enlargements from high resolution digital scans.
When I have examined any year date in minute detail I move on to the next date available and build up a history of change within the site. If the written evidence gives one account I may verify it or contradict it. I often find that people will claim to have pursued some activity on the site but have actually transposed this from another site. Sometimes innocently. And people’s memories about place layouts are often seriously flawed. We are human!
I then use software called Map Maker to produce annotated photoplans of all or the most important and clearest airphotos. The outcome is an incontrovertibly dated list of observed, dated facts about the site, a photoplan showing it all in detail and an opinion that I can swear to and defend in Court or a public enquiry. Judges like the certainty that the airphoto process offers.