The stereoscope was a simple Victorian invention which works on the same principles of today's 3D glasses. It enabled enemy landscape photographs, scanned by teams of photographic interpreters, to be viewed in 3D, and as a result saved thousands from the VI and II missile onslaught.
This BBC articleClick here explains the stereoscope's capabilities.
For those interested, a documentary of "Operation Crossbow" is broadcast at 2100 BST on Sunday 15 May, on BBC Two. The brilliance of our scientists and of the countless men and women involved in World War II will forever be remembered by a grateful nation. TC.
As a qualified PI I was using very similar stereoscopes in the 1980's. There has to be an overlap between photos to get stereo (3D). Some can squint and see 3D without the stereoscope. It doesn't allow you to measure height though. That it is done by knowing the focal length of the camera and the height it was flown at. 3D's advantage is that it can allow you to determine what is a real and what is a fake target.
Nowadays they are Imagery Interpretors viewing digital imagery.
Indeed, you and I know how they were used but that reporter is probably too young. :o)
By the way, after a long search I've found what, or rather who, was causing my posting problem. It was my teenager grandson who has some XP games on my PC playing in Compatibility Mode. In keeping with the modern attitude of some, he had enabled all programs to be viewed/played in CM instead of individual ones, and that made the PCA website jump all over the place. It also gave rise to the very long "Please Wait" situation after posting.
Anyway, the lad has been warned, again, and told to leave my settings alone, or else!! TC.