The relative and absolute geometric algorithm for the ERS baseline estimation

Two fundamental parameters in synthetic aperture radar (SAR) interferometry are baseline orientation and baseline length, which are the key elements of the interferometric geometry. These parameters control how topography is mapped into interferogram phase, and affect the accuracy of the DEM directly. Without ephemeris or the accuracy parameters in it, how to estimate more accurate baseline parameters is an important question. It is an important way to make use of the ground target position in the sub-satellite track, the relative information in the image and other correlative information. In fact, it can estimate the fundamental parameters with the position of the satellite, the difference of two homonymic points´ position, the spatial resolution. etc. Considering the ERS characteristics, the correlative information in the two complex images, and the position of the reference points to the sea level, this paper presents the relative and absolute geometric algorithm to estimate the two parameters. The algorithm is simple in computing, and facile in actualizing. The estimation accuracy is more precise by tests using the ERS data for interferometry.