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In remote sensing, each of the radar and the optical sensor has
its own advantages
over the other. Clearly the synergism of radar data and visible
and reflected infrared
for land resource applications is becoming of greater practical importance. The
objective of this study was to investigate how ERS-1 SAR could effectively
discriminate land cover types in Pu-Li mountain area and Nan-
Tou flat land area and
eventually to determine if the synergism of ERS-1 SAR and TM data could be
achieved to improve significantly the classification accuracies
of land cover types in
these two areas. Statistical analysis and preliminary
interpretation of the radar backscatter
from different land cover types was conducted to establish a
look-up table for surface
features and their signatures on the SAR image. Multispectral
classifications using the
maximum likelihood classifier and accuracy assessment were
performed both on the
composite images and on the TM images. The results showed that
the classification
accuracies of the composite images over Pu-Li and Nan-Tou areas were decreased
slightly with the addition of SAR C band. In the mountain area,
radar backscatter was
dominated by topographic slope due to ERS-1 SAR(s high
depression angle (small local
incidence angle). The within-category variance of each land
cover type became greater
than among-category variance due to the topographic effects
introduced by the high
depression angle. This made ERS-1 SAR C band difficult to
discriminate land cover types
in Pu-Li area. In the flat land area, ERS-1 SAR could not
discriminate land cover types
effectively, since it operates on a single frequency and on a
single polarization mode and
this frequency is not optimal for land cover classification.
Therefore, ERS-1 SAR has poor
discrimination ability for land cover types in these two areas.
Nevertheless, there may have
a high possibility to improve land cover mapping with the
synergistic use of SAR and
visible/infrared data if multi-frequency, multi-polarization
SAR data with an appropriate
depression angle that can minimize topographic effects are
used. The follow-up studies will
be to investigate how to determine an optimal SAR band combination.
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