Abstract: In an airborne SAR system for determining the topography of a terrain, two complete, correlated SAR images with different amplitude modulation in the cross-track direction are obtained and recorded by switching of two antenna patterns which can be generated by means of a monopulse antenna. The desired terrain information is extracted from the amplitude relationship of the two SAR images.It is furthermore possible to extract the terrain information from polarimetric SAR data via crosstalk parameters.

Abstract: In a synthetic aperture radar system, information concerning the radar reflectivity of a point on the ground is placed in an image at an azimuthal (cross-range) position which corresponds to the position of zero Doppler frequency shift of the received signal, under the assumption that the antenna has followed a straight line trajectory. In practice, the antenna trajectory will undergo small deviations about this straight line path which are not taken into account in the azimuth processing and which, consequently, cause incorrect azimuthal positioning in the image of the information concerning a point target on the ground.The invention uses the value of the slope of the frequency modulation of the received signal, calculated by means of an autofocus procedure, to determine the intercept of this frequency modulation at successive azimuth positions.