We have been trying to document changes in vegetation at an experimental wetlands through regular photographs. Each of six wetlands is rectangular in shape and identical in size (approximately 10 m x 20 m). The procedure has been that once/week we climb up a 12' ladder and shoot photos at each corner of each wetland. The problem, of course, is that the shots are taken at an angle and the process of "rubber sheeting them" in GIS to convert these photographs into a square surface for analysis creates substantial distortions. Obviously what we really want is to shoot a photograph from high above the center of each wetland. I would like advice from anyone who has used a small , unpersoned helium balloon or blimp to shoot photos. This is what we would need a system to do:
1) Create high resolution aerial photos -- 3 MB or preferably better. Creating movies is unnecessary. We are solely interested in high resolution snapshots. 2) Be controllable in terms of location such that we can position the camera above the center of each wetland. My thought is that positioning would be by means of tethers from the ground. I see no advantage in a motorized system since it would be harder to get such a vehicle to sit stationary in a fixed position. Minimally, two tethers (probably fishing line on fishing reals) would be necessary for positioning, but perhaps three would be needed 3) The camera needs to situated in a way that ensures that the lens is parallel (level) with the ground in both axes. Perhaps it is fixed to a gimble system to accomplish this. 4) Ideally, it would be possible to view the images on a laptop from the ground while the camera is being positioned. I suppose it might be possible to run a cable all the way up, but I am imagining that even with a wide angle lens, it would be necessary for the vehicle to be 100' or more above the ground surface. That length of cable would add considerable weight. Wireless (blue tooth?), would be ideal if it could be made to work. 5) It must be possible to control shooting from the ground. 6) Ideally, the blimp or balloon must be fairly portable -- something that we might be able to store full of helium somewhere on site so that we can take weekly measures without refilling and deflating each time. 7) Budget is tight -- the whole thing, camera and all, probably needs to be $1K or less. Does anyone have experience with this sort of approach? John Petersen Associate Professor of Environmental Studies and Biology Oberlin College
