The time trajectories of agricultural data points as seen in LANDSAT signal space form a pattern suggestive of a tasselled woolly cap. Using this easily visualized three dimensional construct most of the important phenomena of crop development and observation variables are pointed out, named, discussed and measured. The important crop phenomena described are the distribution of signals from bare soil, the processes of green development, of yellow development, of shadowing and of harvesting. The important external variables include view angle, sun angle, atmospheric haze, and atmospheric water vapor.
The development of a quantitative picture of the tasselled cap depends upon crop and atmosphere effects modeling and upon empirical observation of data signals. Quantitative data from a composite of these sources is given. The tasselled cap structure is illustrated with cluster plots and diagrams.
The tasselled cap is a fertile source of ideas for processing techniques. Examples discussed include
a) A linear preprocessing transformation which isolates green development, yellow development and soil brightness and allows the reduction of the dimension of the feature space.
b) The use of specific measurable pattern elements of the tasselled cap structure to estimate and correct atmospheric haze and moisture effects.
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