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The
next step is to select a band combination that provides
the best enhancement of
features of interest in the image. This step
can range from the very simple (like the three-band color combination
shown here) to the very complex (a statistically derived amalgamation
of several spectral bands, such as a decorrelation stretch or
a Principal Components analysis). The project’s information
needs, and the potential communications use of the image products,
are the primary considerations in determining the best band combination.
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In
this case, ETM bands 7 (reflected near-infrared energy), 4
(another near-infrared band, particularly sensitive to the
presence of chlorophyll and therefore an excellent indicator
of healthy vegetation), and 2 (visible green light) are displayed
in red, green, and blue. This is a “false-color infrared” band
composite that shows excellent differentiation of forested
areas, agriculture, rock and soil types, and human infrastructure
in semiarid regions. Vegetation appears in shades of green,
and water is dark blue.
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