First Results from Multifrequency Interferometry. A comparison of different decorrelation time constants at L, C, and X Band

Abstract

The measurement of displacement from SAR images, using either interferometric or correlation techniques, is always carried out from a comparison between two or more acquisitions separated in time. It is therefore necessary to evaluate the level of phase decorrelation between the two acquisitions in order to understand the quality of the measures that can be obtained. The change of radar resolution cells in time is known to be the main responsible of the gradual decorrelation of the interferometric phase. However, a model that physically describes this process, is at the moment not available. Exploiting the test sites from GITEWS and Exupery, German projects focussed on determination of geo-risks, an analysis of the decorrelation time constants was performed on SAR data from PALSAR, ASAR and TerraSAR-X. Time series of the coherence have been computed and compared with simple statistical models. The time constants were analyzed as a measure of temporal decorrelation, in order to forecast the precision of displacement measures also for future missions. The extracted parameters were finally compared with the type of land covering using optical data and land use maps in order to determine a qualitative relationship between them and extend their validity in a more global context.