Research Methodology - Historical Land Use/Land Cover Classification Using Remote Sensing - page 94

Fig. 5.26 Temporal- and spectral-separability of cotton, corn and watermelon by the third
spectral band of ASTER
Fig. 5.27 The spectral response of cotton, corn and watermelon during the suggested dates to
recognize these summer crops in the spectral range (350-2,500) nanometer
remotely sensed data (e.g., wheat and barley). To overcome this latter problem,
good knowledge of the study area was required in terms of types of crops that were
cultivated, growth stages, the dates of propagation and harvest (agricultural cal-
endar), and the type of farming prevailing, whether irrigated crops/plantations,
rain-fed, or mixed.
''Agricultural crops have rapid changes in spectral characteristics at various
times in the growing season. As, at the beginning of May, wheat planted in the
ERB presents a green canopy of vegetation to the remote sensor, but by late May,
the same wheat will be golden brown and nearing maturity. Two weeks later
between mid and late June, the crop will have been harvested and one will see only
the highly reflective yellow straw. Sometimes, when there has been no tillage or
another crop has been planted, many weeds and green vegetation will be mixed in
with the straw, which could be observed as grazed pasture or perhaps hay. So, it is