were derived by averaging all corresponding pixel values.Fig. 5
showed the results derived from Landsat images on Oct. 13,
1990 and Nov. 1, 2000, respectively.
The results inFig. 5(c) and (d) suggest that the spatial pattern
of the heat islands (areas with relatively high temperatures) has
changed from a scattered pattern (bare land, semi-bare land and
urban area were warmer than other areas) in 1990 to a more
contiguous pattern of urban heat islands in 2000, along with the
expansion of the regional urban system. The centers of high
temperature were consistent with built-up areas, which can
be seen by comparing land use/cover with temperature maps
(Fig. 5, (a) vs. (c), and (b) vs. (d)).
An analysis based on the interpretation of land use/cover
types showed two obvious changes, percentage-wise, between
the two image dates. The percent of built-up area increased from
6.09% in 1990 to 13.08% in 2000, more than doubling the size
of the urbanized areas, while the percent of cropland decreased
from 42.23% to 21.48% for the same time span (Table 3). Much