Compact polarimetric SAR interferometry

The authors discuss the role and performance of compact polarimetry in SAR interferometry. The considered SAR architecture transmits either a linearly polarised wave oriented at 45 degrees or a circularly polarised one, and receives at horizontal and vertical polarisation. Two polarimetric acquisitions are combined in an interferometric image, characterised by a polarimetric and interferometric (POLINSAR) covariance matrix. The expression of the covariance matrix for compact polarimetry is derived and the relationship between compact and full polarimetric covariance matrices is discussed. On the basis of symmetry properties of geophysical media, the authors propose a reconstruction algorithm of the full polarimetric information from a compact polarimetric dataset. The algorithm allows the assessment of compact POLINSAR and the comparison between the two compact configurations. The authors consider forested areas and compare the interferometric degree of coherence measured at different polarisations by compact polarimetry and full polarimetry. The study shows that the degree of coherence from a compact polarimetric architecture carries enough information for POLINSAR applications, such as forest parameters retrieval, if the symmetry properties are satisfied. Airborne data acquired by the DLR E-SAR sensor over the Traunstein forest are used to illustrate the results.