I just talked to my friend who is a gov't defense contractor. He has worked on this FLIR technology. Apparently it is true that marijuana gives off a different wavelength signal while looking from the sky, and this technology is used to find grows. And I am strictly talking about outdoor growing. This technology obviously works concerning indoor growing. I just want to beware outdoor growers that this is a true threat. He mentioned that it is unlikely that they will target small patchy grows, and that they mainly search for the huge grow ops(100-1000 plants).
His suggestion was to make sure to have your plots spread out, 2 or 3 in a group.
hope this helps