Interpretation of a RADARSAT-2 fully polarimetric time-series for snow cover studies in an Alpine context – first results

The aim of the SOAR #1341 project is to perform temporal analyses of changes in RADARSAT-2 full-polarimetry parameters on snow cover in a mountainous area. The objective of the present study was to determine whether there is a correlation between changes in radar statistics and changes in physical snow parameters during winter and spring. This paper focuses on the preprocessing of the images and presents the methodological steps and first results obtained in full polarimetry mode. Six RADARSAT-2 quad-pol images were acquired between January 2009 and January 2010, five in different snow conditions and one snow-free image in summer used as a reference. The fine acquisition mode was selected with a medium incidence angle (39°). A combination of LANDSAT-7 and SPOT optical images and field measurements was used for the validation step. First, RADARSAT-2 images had to be pre-processed due to the influence of high mountain topography on the polarimetric signal: the planned incidence angle was computed using a fine digital elevation model (DEM). Next, the DEM and optical dataset were reprojected onto the slant range mode of RADARSAT-2, the configuration required to preserve the phase signal and polarimetric statistics. Polarimetric analysis was performed using the PolSARpro software from ESA/IETR. The coherency matrices were calculated for each RADARSAT-2 image. Polarimetric descriptors based on the eigenvector–eigenvalue decomposition theorem of this coherency matrix were obtained. The behavior of the Single Eigenvalue Relative Difference, a polarimetric parameter that depends on scattering mechanisms, was analyzed. The polarimetric analysis showed an increase in the multiple scattering mechanism with a dry snow cover compared with the snow-free image. With a wet snow cover, there was an increase in contribution of the single scattering compared with the snow-free image. Our results showed that it was possible to identify temporal changes in dry, wet, or no snow characteristics throughout the winter season by analyzing primary polarimetric decomposition parameters and by comparing them with measurements made at 10 field sites.

[1]  Martti Hallikainen,et al.  The use of ERS-1 SAR data in snow melt monitoring , 1997, IEEE Trans. Geosci. Remote. Sens..

[2]  C. Swift,et al.  Microwave remote sensing , 1980, IEEE Antennas and Propagation Society Newsletter.

[3]  Jiancheng Shi,et al.  Snow mapping in alpine regions with synthetic aperture radar , 1994, IEEE Trans. Geosci. Remote. Sens..

[4]  Richard K. Moore,et al.  Radar remote sensing and surface scattering and emission theory , 1986 .

[5]  Helmut Rott,et al.  Retrieval of wet snow by means of multitemporal SAR data , 2000, IEEE Trans. Geosci. Remote. Sens..

[6]  J. Dedieu,et al.  Radiometric and geometric correction of RADARSAT-1 images acquired in alpine regions for mapping the snow water equivalent (SWE) , 2003, IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477).

[7]  Thomas H. Painter,et al.  Retrieval of subpixel snow covered area, grain size, and albedo from MODIS , 2009 .

[8]  Laurent Ferro-Famil,et al.  Unsupervised terrain classification preserving polarimetric scattering characteristics , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[9]  Eric Pottier,et al.  Quantitative comparison of classification capability: fully polarimetric versus dual and single-polarization SAR , 2001, IEEE Trans. Geosci. Remote. Sens..

[10]  Jean-Pierre Fortin,et al.  The potential of times series of C-Band SAR data to monitor dry and shallow snow cover , 1998, IEEE Trans. Geosci. Remote. Sens..

[11]  Adrian K. Fung,et al.  Modelling of microwave emission and scattering from snow and soil , 1989 .

[12]  F. Ulaby,et al.  Dielectric properties of snow in the 3 to 37 GHz range , 1986 .

[13]  H. Rott,et al.  The analysis of backscattering properties from SAR data of mountain regions , 1984 .

[14]  Yves Durand,et al.  NEW INVERSION METHOD FOR SNOW DENSITY AND SNOW LIQUID WATER CONTENT RETRIEVAL USING C-BAND DATA FROM ENVISAT/ASAR ALTERNATING POLARIZATION IN ALPINE ENVIRONMENT , 2007 .

[15]  Mingquan Lu,et al.  Improved Zero-Padding Method for Rapid Long PN-Code Acquisition , 2008, IEEE Transactions on Signal Processing.

[16]  Ramata Magagi,et al.  Optimal conditions for wet snow detection using RADARSAT SAR data , 2003 .

[17]  N. Baghdadi.  Capability of multitemporal ERS-1 SAR data for wet-snow mapping , 1997 .

[18]  A. Wiesmann,et al.  Microwave Emission Model of Layered Snowpacks , 1999 .

[19]  Helmut Rott,et al.  SNOW CLASSIFICATION ALGORITHM FOR ENVISAT ASAR , 2005 .

[20]  Laurent Ferro-Famil,et al.  A polarimetric classification from PolSAR data using SERD/DERD parameters. , 2006 .

[21]  Jiancheng Shi,et al.  Inferring snow wetness using C-band data from SIR-C's polarimetric synthetic aperture radar , 1995, IEEE Trans. Geosci. Remote. Sens..

[22]  Jiancheng Shi,et al.  Measurements of snow- and glacier-covered areas with single-polarization SAR , 1993, Annals of Glaciology.

[23]  J. Zyl,et al.  Unsupervised classification of scattering behavior using radar polarimetry data , 1989 .

[24]  J. Dedieu,et al.  Dry snow discrimination in alpine areas from multi-frequency and multi-temporal SAR data , 2006 .

[25]  David Riaño,et al.  Assessment of different topographic corrections in Landsat-TM data for mapping vegetation types (2003) , 2003, IEEE Trans. Geosci. Remote. Sens..

[26]  J. S. Lee,et al.  A review of polarimetry in the context of synthetic aperture radar: concepts and information extraction , 2004 .

[27]  Jiancheng Shi,et al.  Deriving snow liquid water content using C-band polarimetric SAR , 1993, Proceedings of IGARSS '93 - IEEE International Geoscience and Remote Sensing Symposium.

[28]  Audrey Martini,et al.  Télédétection d'un couvert neigeux en milieux alpins à partir de données SAR polarimétriques multi-fréquentielles et multi-temporelles , 2005 .

[29]  P. Teillet,et al.  On the Slope-Aspect Correction of Multispectral Scanner Data , 1982 .

[30]  Jeff Dozier,et al.  Snow Mapping and Classification from Landsat Thematic Mapper Data , 1987, Annals of Glaciology.

[31]  Stephen L. Durden,et al.  A three-component scattering model for polarimetric SAR data , 1998, IEEE Trans. Geosci. Remote. Sens..

[32]  Eric Pottier,et al.  An entropy based classification scheme for land applications of polarimetric SAR , 1997, IEEE Trans. Geosci. Remote. Sens..

[33]  A. Fung.  Microwave Scattering and Emission Models and their Applications , 1994 .

[34]  Simon Yueh,et al.  CoRe-H2O - A dual frequency SAR mission for hydrology and climate research , 2007, 2007 IEEE International Geoscience and Remote Sensing Symposium.

[35]  Helmut Rott,et al.  Multifrequency and polarimetric SAR observations on alpine glaciers , 1993 .

[36]  Eric Pottier,et al.  A review of target decomposition theorems in radar polarimetry , 1996, IEEE Trans. Geosci. Remote. Sens..

[37]  Lars M. H. Ulander,et al.  Radiometric slope correction of synthetic-aperture radar images , 1996, IEEE Trans. Geosci. Remote. Sens..

[38]  Yoshio Yamaguchi,et al.  Numerical methods for solving the optimal problem of contrast enhancement , 2000, IEEE Trans. Geosci. Remote. Sens..

[39]  Jiancheng Shi,et al.  The effect of topography on SAR calibration , 1993, IEEE Trans. Geosci. Remote. Sens..

[40]  Laurent Ferro-Famil,et al.  Unsupervised classification of multifrequency and fully polarimetric SAR images based on the H/A/Alpha-Wishart classifier , 2001, IEEE Trans. Geosci. Remote. Sens..

[41]  E. Pottier,et al.  Polarimetric Radar Imaging: From Basics to Applications , 2009 .

[42]  Laurent Ferro-Famil,et al.  Snowpack Characterization in Mountainous Regions Using C-Band SAR Data and a Meteorological Model , 2009, IEEE Transactions on Geoscience and Remote Sensing.

[43]  L. Rabiner,et al.  A digital signal processing approach to interpolation , 1973 .

[44]  H. Zebker,et al.  Imaging radar polarization signatures: Theory and observation , 1987 .

[45]  Christian Mätzler,et al.  Snow mapping with active microwave sensors , 1984 .

[46]  J. Dozier.  Spectral Signature of Alpine Snow Cover from the Landsat Thematic Mapper , 1989 .

[47]  Jiancheng Shi,et al.  Mapping seasonal snow with SIR-C/X-SAR in mountainous areas , 1997 .

[48]  Hermann Kaufmann,et al.  Comparison of Topographic Correction Methods , 2009, Remote. Sens..