Abstract
Abstract. Synthetic Aperture Radar (SAR) data can be difficult to interpret over glacierized terrain, especially in areas of high relief where most of the smaller glaciers of the world are found. The two primary objectives of this paper are to correct the topographically induce distortions inherent in SAR image of rugged terrain and to map glacier facies in the corrected polarimetric (PolSAR) image. Methods for terrain correction of PolSAR developed in this paper, which base on the coherency matrix data, utilize polarimetric signature to refine the location accuracy and perform the pixel size normalization on each element of the coherency matrix using the backward integration method. Moreover, azimuth-slope correction is immediately following after radiometric correction. A supervised classification is performed on the orthorectified image to map the spatial distribution of snow and ice. The visual boundary between wet snow and bare ice surface is delineated on the orthorectified image too. These results show that glacier facies and the wet snow line can be mapped reasonably well using Radarsat-2 PolSAR in a mountainous environment.
Highlights
As it not affected by cloud covers and has ability to penetrate beneath to ice/snow surface to observe the subsurface structure, Synthetic Aperture Radar (SAR) has been successfully applied to monitor the Mountain Glaciers due to its high spatial resolution and wide coverage(Henderson and Lewis, 1998)
By extracting a profile of the polarization orientation angels along the central flow line of Big Dongkemadi Glacier, we investigate the difference of the orientation angles derived by digital elevation model (DEM) directly and circular polarization method
The geocoding accuracy was evaluated by visual checking the overlap between DEM and the SAR image in figure 7
Summary
As it not affected by cloud covers and has ability to penetrate beneath to ice/snow surface to observe the subsurface structure, SAR has been successfully applied to monitor the Mountain Glaciers due to its high spatial resolution and wide coverage(Henderson and Lewis, 1998). Fully PolSAR systems such as Radarsat-2(C-band) and PALSAR (L-band) have been launched These new instruments promote the detection and monitoring capabilities of glacier facies as the polarimetry contain information on the structural characteristics (shape and orientation) of the scatterer and enable us to better discriminate between volume and surface scattering and to properly indentify the different glacier facies. When trying to monitor the snow characteristics and map glacier facies from PolSAR data in a mountainous environment like Mountain glaciers in western China, radiometric corrections must first be applied to correct for the distortions induced by the slant projection of SAR systems and by the highly variable terrain. A supervised classification is performed on the orthorectified PolSAR to map the spatial distribution of snow and glacial ice and evaluate the detection and monitoring capabilities of glacier facies with PolSAR. We first introduce the test site and experimental datasets, and describe the algorithms and processing steps involved in our method on terrain correction and mapping glacier facies, and present some technical remarks and conclusions
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