Detecting Small-scale Topographic Changes and Relict Geomorphic Features on Barrier Islands using SAR
POLSAR Results
During this project, we demonstrated that POLSAR data are able to separate various
sub-environments and morphological features very well. In general, we found that C-band is well suited for detailed vegetation discrimination, whereas L- and P-band are better for separating the imagery into larger scale environmental units based on both vegetation and substrate characteristics.
L-band appears to best delineate beach ridge and swale morphology. L- and P-band data appear to indicated extensions of tidal creeks cutting across the islands that may not be visible on aerial photography. L- and P-band can also delineate former breaches caused by storms and dredging.
TOPSAR Results
The figure shown above is a 1996 DEM of the southwest end of Bolivar Peninsula which was obtained with the C-band, 40 MHz TOPSAR with radar illumination from the Gulf of Mexico. The azimuth (flight path) direction is roughly parallel to the peninsula. Maximum relief of this region is about 6 m. The shading interval is 9 cm and the spatial resolution of the pixels is 10 m by 10 m.
Topographically subtle features such as the beach face, foredune, beach ridges and swales, and an old railroad grade are apparent. There are, however, vertical bands which are a systematic error caused by aircraft motion.
The figure above is a transect taken from the DEM in the previous figure. This transect crosses the zone where waves are breaking, the beach, dune, beach ridges, tidal creek, and the intracoastal waterway (ICW). Areas where there is a smooth surface (such as the bays and the ICW), the radar backscatter is low. In these areas, therefore, the signal to noise ratio for the TOPSAR is low resulting in noisy heights. The transect shows the ocean height at the beach face, the height of the tidal creek, the heights of the ICW shorelines, and the height of the bay shoreline all to be within 20 cm, which is expected. This result indicates the internal consistency of the DEM. For this reason, it is expected that the TOPSAR DEM's are useful for aiding the classification of
sub-environments in low-relief coastal areas.
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Last Modified: Wed Apr 14, 1999
CSR/TSGC Team Web
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