Very cool idea. Never heard that trick. I have heard of people seeing foundation outlines by frost on the ground before. The foundation blocks or stones would hold the heat longer than the surrounding dirt, so when there is an early morning frost you could see the areas where frost didn't form on the grass showing the outline of the foundation.
I've got some pictures below I think you guys might find interesting on spotting old signs of foundations/trails/old roads/etc. And no it's not google earth. This is better! And you can always get the view your looking for right up to date on that day with the change of seasons you want for no leaves on the trees and such to see into the canopy easier, or in the spring for say spotting apple trees in bloom in the woods which is often a sign of an old homestead long since gone.
A way I've been messing around with here and there (not much lately though) is kind of along the same lines of what your are talking about. I design and build my own electric RC aircraft using high performance brushless motors and lipos, so depending on the design and wing loading I can lift some pretty hefty payloads into the air on certain planes. One plane I designed specifically for housing my digital pocket camcorder/camera. I can either do still shots triggered remotely by my remote control plane transmitter control, or I can also do live video recording along with live video feed to the ground so I can watch the view as if I were the pilot and also what I'm filming or taking pictures of.
This bird's eye view can reveal details and clues to old activity in the area that would be very hard if not impossible to notice from on the ground. Old roads or trails that the forest canopy shows you slight evidence of, old foundations that just have very slight elevations or depressions to outline them compared to the surrounding ground, and so on. It's also a handy way to scout from a bird's eye view to see if any private land might be worth asking permission to hunt on if you can see some old structures off in the distance that would be impossible to see from the ground due to trees or other obstacles. Once you find something that looks worthy of hunting it motivates you to knock on a door and ask permission, and since you've probably found something nobody else would have ever seen from the road chances are it's never been detected before.
A friend has taken the video fly by wire to the next step. He's gone onto what they call FPV (First Person View). He built goggles with LCD screens in them so that he sees with his eyes and has the experience of actually being the pilot in the plane. He can turn his head left or right and the camera on the plane will pan in that direction just like you are looking out the window! Very cool stuff. I could do that but the only problem is if you should lose your video feed and need to remove the goggles to find the plane, it's very hard to find an RC plane in the air once you've taken your eyes off it from experience talking. And also, often he flies his plane so far off in the distance that you could never see it by the naked eye anyway should there be a video feed problem. I prefer to keep my real eye on the plane at all times and only take small glances at my display screen to see what the plane is seeing to line up shots and such. I can always land the plane and review the recorded video or still shots for any hints of possible metal detecting sites.
I hotwire my planes from construction foam, and then greatly re-enforce things like the wings with carbon tubes or sheet things with balsa for added crash protection. My yellow aerial design below has a bulky body because I wanted my camera well protected in the event of a crash. I can get a good half hour or so of flight time with throttle management. Full throttle mostly about ten to fifteen minutes or so. All depends on how much you gun the electric motor. These brushless motors are very powerful, creating a lot of torque and speed, and very efficient, so using high capacity lipo batteries you can get some very long run times out of them.
The yellow plane is the design I made for my RC video applications, but the red dual boom pusher is another design I really to fly for it's stability as well and it's unique abilities to turn on a dime and get out of a closed in situation, like misjudging the height of a tree in it's path. Thanks to it's large control surfaces such as the horizontal and vertical stabilizers, it's got very good control and stability at even almost walking speeds with little air flow over the control surfaces, and it literally seems like I can pull the nose up on that plane and kick the tail around and it will stop and spin around on a dime in one spot. For it's fantastic manoeuvrability I think it would also make an excellent aerial platform and may build another in similar design for aerial video specifically down the road as well.
Great thing about foam is it is cheap, easy to work with, fast to build with, and you can hot wire out pretty much any design you can think up in your head, along with it being very light, very durable, and it repairs real easy with a little Gorilla Glue. Gorilla Glue will foam into the crevices of the foam and make a really solid repair, and it's light like foam too once dry due to all the trapped air in it.
Anyway, the pics...You can see some of my aerial still shots below over a old farm I had permission to be on. Note the old red barn and the trails through the fields to indicate how old foot trails from eons ago can be very visible from the air but hard to see on the ground too.
The delta wing stealth looking plane is the only one I didn't build the body for. It's my speed demon and will do close to 100mph or so. Scares me to fly sometimes and hard to keep an eye on and figure out orientation at full throttle some times. We custom winded the brushless motor with a friend's own specifications and it really gets up and goes with some very efficient amp draw for how fast it'll go...