We propose in this paper an original method to correct the geometric distortions of a radar image. The comparison of satellite data, reveals specific problems. Data can be noisy, but especially the geometry of their acquisition requires corrections for comparaisons between them. In this paper we show how highly deformed radar images can be geometrically corrected and compared to map data coming from digital terrain models and also with data coming from SPOT satellite. Radar images used, are from the sensor airborne radar Varan, which is used for data acquisition campaign in the SouthEast of France. Applications include both structural geology, land cover or study of coastline. We propose a solution to rectify radar image in the geometry of a numerical terrain model. The method adopted here, is to produce a synthesis radar image by encoding all flight parameters of aircraft or satellite from a digital terrain model; radar image can then be compared to the synthetic image because points of landmarks can be clearly identified. Finally, we obtain a correspondence between the points of real radar image distorted, and those in the land or map.