From a writer who knows things:
I just don't buy the crop circle/satellite story. In the first place, there are large objects all over the world with known dimensions. No point in measuring a crop circle in Kansas to gauge a rocket launching pad outside Moscow. Would make better sense to gauge it against, say, the width of the Kremlin.
If the pictures were to be of the U.S. any known structure could be a gauge (Hoover Dam, White House, Golden Gate Bridge).Crop circles were, I believe, fairly small as compared to other available structures that could be used without fucking up a farmer's field. Their image size would be extremely small and hard for an intelligence analyst to use and the contrast of the circle compared to the surrounding field is low.
I just don't see how practical a crop circle would be since crops grow back.I'm not suggesting UFOs or anything like that is the cause. With my background in intelligence/aerial photography and photogrammetry it just doesn't ring true to me.
Just thought of another way. Measure a distance on a straight piece of highway and paint a line at each end. Voila, a precise calibration meter that requires no clandestine crop chopping with possible discovery by a supremely pissed farmer.
The other thing is that a ground calibration is not necessary at all. There is a mathematical solution involving the ratio between the camera lens focal length and film size compared to the altitude above the ground. If you have these three dimensions you can precisely figure the fourth -- the area covered on the ground. Simple algebra. So when you know the dimension of the patch of ground in the picture simply draw a ratio between the ground covered and the object image size.
This simple "mapping math" has been used for years by photographers and analysts for such things as aerial reconnaissance from jet planes and others. In Antarctica, before satellite coverage was readily available, the navy squadron (VX-6) mapped the entire continent using aerial cameras mounted in C-130 Hercules and C-121 Constellation airplanes. The film went to the US Geodetic Survey where the pictures were laid in a mosaic and maps were produced. Imagine the effort that went into it and the difficulty involved in doing this multi-year project. The task was completed (the photography part) around the mid-to-late 1960's. Later, satellites did the same job in a week or so.
Want more? Google "Talent-Keyhole". It is a now declassified Top Secret code word for the Corona program. Satellite pictures in film cans dropped into the atmosphere and caught by airplanes. This was something I used in a novel.