POL-InSAR Forest Techniques and Applications by means of TanDEM-X new Results and Experiments

Abstract

Polarimetric Synthetic Aperture Radar Interferometry (Pol-InSAR) has been proven to be a powerful radar remote sensing technique for the investigation of natural volume scatterers. The coherent combination of single- or multi-baseline interferograms acquired at different polarisations provides sensitivity to the vertical distribution of scattering processes and allows their characterisation by using the associated (volume) interferometric coherences. However, in repeat-pass spaceborne implementations, the inherent presence of temporal decorrelation is biasing the interferometric coherence estimates degrading the sensitivity to vertical scattering structure and limiting the performance of Pol-InSAR inversion techniques. This is the main reason why polarimetric space-borne missions could not contribute essential neither with respect to large scale demonstration of Pol-InSAR techniques nor for the development of new Pol-InSAR applications areas [6]. TanDEM-X – successfully launched in June 2010 – forms together with TerraSAR-X the first single-pass polarimetric interferometer in space. This allows for the first time the acquisition and analysis of Single-, Dual-, and Quad-Pol-InSAR data without the disturbing effect of temporal decorrelation. Even if X-band has - when compared to lower frequencies - a reduced penetration capability recent airborne experiments demonstrated several cases where a rather surprising penetration into natural volume scatterers - as vegetation and ice - could be proven. In this sense, the investigation of the Tandem-X Pol-InSAR data sets will strongly contribute to our understanding of scattering processes at X-band and potential new Pol-InSAR applications.