Over the weekend I watched a documentary called The Last Heroes of D-Day, and in episode one they discuss flying the complete coast line of France taking photography from 30,000 feet. They were able to see everything that the German military was doing to fortify the coast, and see where the best places to land would be. Then they used stereo photography techniques to get a 3-D picture of the complete coast line in order to see how high cliffs were and looking a circles they could see that they were actually smoke stacks for industrial plants. They were able to see the lay of the country side down to the tree and hedge row in order to plan movements and see swampy areas in the planning. It was really well done by the BBC. It was amazing the remote sensing that was done.