FWIW, they've been taking pix like that ever since, oh, I don't know,
something like the 50's? The military takes the pix to keep tabs on us and
the rest of the world. Former Russia and a number of other countries do the
same thing. They take the photos with satellites and with high-altitude
aircraft. The stuff that we don't get to see..... well, from what I've
heard, the military can tell what kind of tie you're wearing just from their
satellite cameras.
What really pisses me off is that our (U.S.) Gov't. puts a false error into
the signal that civilian GPS models receive. They say that this is to keep
militia, etc. from using precise (up to 3m) coordinates to bomb somebody or
something, but that is just "feel-good" politics. The Russians have the
same GPS system that the U.S. does, and they don't have the error. So, I
guess if you wanted really accurate GPS coordinates, you could go buy a
Russian system. Your accuracy won't get much better than 3m (due to the
ionosphere - the part of our atmosphere responsible for Aurora borealis -
bending the signal). However, with a Master/Slave GPS setup and/or a
connection to LORAN or other trueing system, you can get very close. I know
some guys that work for the U.S. Army Corp of Engineers - they use $20K+ GPS
units that can get within 1cm horizontal, 3cm vertical.
With the Master/Slave setup, one (master) GPS remains at known coordinates,
while the other (slave) GPS is used to make measurements, etc. In a
real-time system, the two units communicate with each other - the Master has
a known error rate (since it is stationary at known coordinates) and
translates the correction to the traveling GPS unit.
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