I wonder how they got the altitude. Balloon or tower or what? I presume they traced out the lines on the ground, maybe
with different colors for the different colored shirts the troops wore. This was before a lot of radio gear was around, so
perhaps this was all done by megaphone. I wonder how long it took to arrange and shoot this. They may have started
before dawn to have the daylight at the correct angle. I bet it was done on one of those big negative cameras, which is
why you can pick out the individual heads, if not faces. It was a good way to keep troops out of trouble.