Kevin Lee Hayes wrote his master's thesis on this topic. Copies are available through the links at the bottom of this page.
Below is a Digital Color Infrared image (DCIR) Taken with a Kodak
DCS420ir camera equipped with a bandpass filter. This was taken at
about 1,000 feet above ground level. Useful images may be taken from
much higher altitudes. Using spectral analysis techniques, a tremendous
amount of data may be gleaned from this kind of image. These images
are much more useful to a variety of users than plain film, shown further
down the page. Digital images are cheaper, faster, and easier to
send all over the world. Smaller images can be attached to e-mail,
sent to FAX machines and put on floppies. Many large images are better
stored on ZIP disks. A CD reader is handy for reviewing many of these
large and detailed images. Ordinary 'picture' software is ok for
looking at these, but advanced image processing packages can bring out
many features and kinds of data not readily seen by the eye.
(That is what I do!)
Below is a conventional Color Infrared film (CIR) image, scanned at 600 dpi, from Kodak 2443 aerial photo film. Even with a histogram stretch applied, it does not have the variety of tones found in the digital image above. It takes a bright day to acquire this kind of film based product, and the film processing is expensive. Scanning is extra, and may lose detail. This particular image was taken at 4,300 feet above ground level. Species are difficult to identify, but detail is excellent. Shadows are more useful for finding dead trees and snags. Slower shutter speeds result in more motion-induced blur at low flying heights.
What we really need is an inexpensive UAV to fly the camera through
our study areas. The advantage would be lower flying height, greater
safety, and lower costs. An aircraft able to follow GPS waypoints
through a grid would be most helpful. HAM amature frequencies will
be needed, and it will take an 8-foot wingspan. The plane's structure
will have to be optimized for protecting the expensive camera package.
I am currently researching this low-cost technology for vegetation analysis.
Kevin Lee Hayes