Soil moisture retrieval over agricultural fields from multi-polarized and multi-angular RADARSAT-2 SAR data |
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Authors: | Imen Gherboudj Ramata Magagi |
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Affiliation: | a Université de Sherbrooke, Centre d'applications et de recherches en télédétection (CARTEL), 2500 Boulevard de l'Université, J1K 2R1, Sherbrooke, QC, Canadab University of Guelph, Department of Geography, 50 Stone road East, N1G 2W1, Guelph, Ontario, Canadac Environment Canada, MSC Hydrometeorology and Arctic Lab, 11 Innovation boulevard, S7N 3H5, Saskatoon, SK Canada |
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Abstract: | The aim of this study was to estimate soil moisture from RADARSAT-2 Synthetic Aperture Radar (SAR) images acquired over agricultural fields. The adopted approach is based on the combination of semi-empirical backscattering models, four RADARSAT-2 images and coincident ground measurements (soil moisture, soil surface roughness and vegetation characteristics) obtained near Saskatoon, Saskatchewan, Canada during the summer of 2008. The depolarization ratio (χv), the co-polarized correlation coefficient (ρvvhh) and the ratio of the absolute value of cross polarization to crop height (Λvh) derived from RADARSAT-2 data were analyzed with respect to changes in soil surface roughness, crop height, soil moisture and vegetation water content. This sensitivity analysis allowed us to develop empirical relationships for soil surface roughness, crop height and crop water content estimation regardless of crop type. The latter were then used to correct the semi-empirical Water-Cloud model for soil surface roughness and vegetation effects in order to retrieve soil moisture data. The soil moisture retrieved algorithm is evaluated over mature crop fields (wheat, pea, lentil, and canola) using ground measurements. Results show average relative errors of 19%, 10%, 25.5% and 32% respectively for the retrieval of crop height, soil surface roughness, crop water content and soil moisture. |
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Keywords: | RADARSAT-2 Polarization ratios Modelling Empirical relationships Ground measurements Agricultural fields Crop height Crop water content Soil surface roughness Soil moisture |
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