Image Processing Reference
In-Depth Information
water temperatures when the image was recorded in the morning of March 6, 2001.
Slightly negative vegetation fractions in the Kuwait City image correspond to bare
soil that are not accurately represented in the three endmember mixture model. The
vegetation fractions in New York City are generally lower than 0.75 as most of the
vegetation takes the form of deciduous trees which have as much as 25% internal
shadow from canopy structure. In contrast, vegetation fractions in Kuwait City are
less that 0.45 because most of the vegetation patches are much smaller than the 30 m
IFOV of the ETM+ sensor.
More land cover categories, identified by locating the geographic position of the
pixels in each part of the mixing space, are observed in the New York City than the
Kuwait City image primarily due to the morphology and location of the two cities
as mentioned previously. Apart from a few tall buildings in the central business
district area in the upper-central part along Kuwait Bay, the majority of houses in
Kuwait City consists of one or two storey buildings which could be residential,
commercial or both. The study area in New York City on the other hand consists of
several residential areas with 2-20 story buildings and commercial districts con-
taining tall buildings creating urban canyons.
Chapter Summary
The world's population growth in urban areas will continue to escalate and
have a profound effect on environmental conditions and processes. Urban
sprawl presents several challenges in the area of land use planning, housing,
pollution and development, and changes in microclimate. The most success-
ful applications of remote sensing to the urban environment generally involve
measurement of physical quantities related to environmental conditions such
as vegetation abundance and surface temperature. Urban data recorded by
operational satellites such as Landsat and SPOT consist of spectrally mixed
pixels because of the relatively coarse satellite resolution than individual fea-
tures in urban mosaics. Spectral mixture analysis provides a physically based
system to quantify spectrally heterogeneous urban reflectance. Vegetation
fraction images are generated from a three-component mixing model based
on high albedo substrate, vegetation and dark surface that is physically con-
sistent with the spectral characteristics that might be expected for an urban
environment. Surface temperatures can be derived from satellites' thermal
infrared measurements through Planck's law. Surface temperature distribu-
tion and vegetation fraction analysis using Landsat ETM+ data reveal the
different energy flux and surface properties for New York City and Kuwait
City, located in temperate and desert environments, respectively. Scatterplots
of surface temperature and vegetation fractions define the physical limits
imposed by the vegetation cover, soil water content, and different combina-
tions of surface materials in each city.
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