Environmental Engineering Reference
In-Depth Information
0-10%
10-20%
20-30%
30-40%
40-50%
50-60%
60-70%
70-80%
80-90%
90-100%
0.3-0.6
Water
0-0.15
0.15-0.3
0.6-0.85
0.85-1.0
Figure 5.10
The subpixel frequency distribution of vegetation cover estimated using the Polya function. This figure shows the
probability (values in the legend) of each level of percent vegetation cover if the cover within each large pixel is measured using scale
(subpixel size) of 30m.
several important environmental parameters to fit the
scales of environmental models, the resultant values can
be greatly improved and promising. An environmental
model is generally complex and related to several types
of parameters, so it may be necessary to combine several
scaling techniques to scale both parameters and models
for the reduction of scale uncertainties. This procedure
has been demonstrated in the modelling of soil erosion at
the global scale. However, we need to pay more attention
to the following issues:
•
Few scalingmethods have dealt effectively with intrinsic
environmental behaviour at regional and global scales
because our solid knowledge remains on the local
processes. More efforts are needed to develop the tools
and techniques to integrate data sources and to operate
models at multiple scales.
•
With the rapid increase of environmental datasets,
particularly satellite-derived environmental parameters
from multiple scales and multiple sensors, data quality
and data continuity constrain the applications of spatial
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