In the last decades, the growing interest in the field of homeland security and the risk monitoring, associated with natural and human induced hazards, has boosted the development of advanced radar techniques for generating high resolution radar images. Inverse and direct Synthetic Aperture Radar (ISAR/SAR) are two well radar techniques which exploit the relative motion between the target and the sensor for generating high resolution radar images of the target of interest. In this thesis a novel ISAR autofocus technique has been addressed by exploiting the estimation of the radar signal Doppler parameters. It has been tested on real datasets, and, the experimental results have been compared with the Image Contrast Autofocus Technique. Furthermore, a procedure for the mitigation of the atmospheric delay variation, which represents a main limitation for the detection and the monitoring of weak deformation patterns in Differential SAR Interferometry (DInSAR) has been discussed. It is based on the integration of GPS atmospheric delay measurements in the multipass DInSAR processing chain. The newest algorithm has been tested on post-seismic deformation occurring in the area of L'Aquila (Italy), hit by a critical seismic sequence in 2009.