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Geometric and radiometric calibration of synthetic aperture radar images acquired in alpine regions-spaceborne and airborne

Multi-temporal synthetic aperture radar (SAR) images acquired in alpine regions by spaceborne and airborne instruments are radiometric and geometric calibrated using corner reflectors, high precision digital elevation model (DEM) and orthophoto images. A fully automatic procedure are developed and applied to multi-temporal series of images acquired from the Norwegian test site of the EMAC'95 campaign. The results show that the entire SAR data set can be calibrated to the required precision even in highly topographic areas by using the repeat coverage and a high precision DEM. The RMS geometric errors are 7 m for the airborne data set and 15 m for the ERS data set. Radar cross-section versus incidence angle is established and consistency is achieved between airborne and spaceborne data. The calibrated data are used for investigating the potential of SAR instrument for snow monitoring in alpine regions.