Multi-baseline polarimetric SAR interferometry -: first experimental spaceborne and airborne results

This paper gives an introduction to multi-baseline polarimetric synthetic aperture radar interferometry (Pol-InSAR) and shows experimental results obtained with a spaceborne and an airborne SAR system. Conventional InSAR combines two SAR images of the same scene acquired from slightly different viewing angles. Pol-InSAR improves the performance of scalar InSAR by exploiting the wave polarisation, allowing a more sophisticated physical interpretation of SAR interferograms. The interferometric decomposition permits the identification of arbitrary scattering mechanisms in two interferometric SAR images and the optimisation of the interferometric coherence, using the identified mathematically independent phase centres related to these scattering mechanisms. Pol-InSAR is sensitive to the distribution of oriented objects in vegetation layers. It is demonstrated that the calculated scattering mechanisms have different vertical loci that can be related to certain vegetation structures. This technique allows for a more appropriate reconstruction of the quasi-three-dimensional spatial distribution of such scattering processes within natural media. Further, the effect of the baseline on the estimation of these scattering mechanisms is shown for the interferometric decomposition. Finally, the differential interferometric phase is calculated between the associated scattering mechanisms for all interferometric pairs and different polarisation states. (C) 2002 Elsevier Science B.V. All rights reserved.