Radar Imaging using SAR systems provides specific information that is very useful in the frame of “Digital Earth ” applications (i.e. flood supervision, forestry or agriculture watch,). The main interest of such active systems is their capability to gather relevant data whatever the weather and the illumination conditions may be (cloudy, misty, during the night,). In addition, these systems give a useful “distance map ” thanks to the wave coherence. Most applications require a follow-up of the situation during weeks or months. Such a follow-up can only be performed if we are able to register images captured at different times. This registration problem is a very classical one and has been widely studied in Remote Sensing, but the proposed solutions are often dedicated to specific contexts (sensors, type of scenes, known relevant elements).Many algorithms have been proposed to register SAR images, and we give, in this paper, a global overview of these methods depending on the chosen approach. They may use filtering or not prior to registration, and they may use landmarks or not; but, in all cases, there will be to take into account the speckle that reduces the efficiency of classical methods for extracting features (e.g. landmarks,) to be paired in both images. During the last years (since 2000), a new set of methods, related to the Hough Transform concept, have been proposed: the algorithm we introduce in this communication can be considered as being in this class of approaches.