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Satellite
information products readily provide evidence on whether agricultural
land has been cultivated, used as pasture, or set aside. This
evidence can help with claims for subsidies and grants.
Multispectral data provides the most useful information
for vegetation studies as it is able to indicate the location
and state of growth. In an RGB-432 colour composite, the
level of red generally indicates the presence of healthy
vegetation due to the 'red-edge' ratio created by a high
chlorophyll content, and blue indicates the extent of soil
exposure.
Detailed analysis may also reveal information about the
state of health of crops, their stage in the phenological
cycle, and biomass level, as well as differentiating between
different crop types. Seasonal changes are thus very important
when interpreting agricultural satellite imagery, and must
be considered carefully when choosing the data.
The image shown is an RGB-457 colour composite of Landsat
TM imagery near London. Fields can be easily delineated,
with colours ranging from blues and greens to orange, depending
on their vegetation content. Wooded areas are dark brown,
with the smooth greens of a golf course highlighted within
a forested area to the southwest of the image.
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