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| Titel |
Use of ENVISAT ASAR Global Monitoring Mode to complement optical data in the mapping of rapid broad-scale flooding in Pakistan |
| VerfasserIn |
D. O'Grady, M. Leblanc, D. Gillieson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 15, no. 11 ; Nr. 15, no. 11 (2011-11-17), S.3475-3494 |
| Datensatznummer |
250013026
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| Publikation (Nr.) |
 copernicus.org/hess-15-3475-2011.pdf |
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| Zusammenfassung |
| Envisat ASAR Global Monitoring Mode (GM) data are used to produce maps of the
extent of the flooding in Pakistan which are made available to the rapid
response effort within 24 h of acquisition. The high temporal frequency
and independence of the data from cloud-free skies makes GM data a viable
tool for mapping flood waters during those periods where optical satellite
data are unavailable, which may be crucial to rapid response disaster
planning, where thousands of lives are affected. Image differencing
techniques are used, with pre-flood baseline image backscatter values being
deducted from target values to eliminate regions with a permanent flood-like
radar response due to volume scattering and attenuation, and to highlight the
low response caused by specular reflection by open flood water. The effect of
local incidence angle on the received signal is mitigated by ensuring that
the deducted image is acquired from the same orbit track as the target image.
Poor separability of the water class with land in areas beyond the river
channels is tackled using a region-growing algorithm which seeks
threshold-conformance from seed pixels at the center of the river channels.
The resultant mapped extents are tested against MODIS SWIR data where
available, with encouraging results. |
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