Different band combinations can be used to bring out various characteristics in the environment. The top two maps here use two different combinations of Landsat satellite imagery. The NVDI map uses a False Color image composite, which joins bands 2,3, and 4. When the NVDI process is added, the negative ouputs show up as red. Bare rocks, sand, and snow have an output close to zero, and those with a higher measure of "greenness" have higher values. This allows dense vegetation, like tropical rainforest, to show up clearly. The combination of bands 4,5, and 1 in the second map is used to differentiate vegetation that is stressed and sparse with healthy vegetation.
The map at the bottom shows a map resulting from a supervised classification, First a training signature file was created by drawing polygons around samples of each class. Known Mayan pyramid sites were used to create this class's sample. The classification shows the locations of possible new sites, and creates a tool to be used in survey and ground-truthing.
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