Inversion of Vegetation Parameters Based on Polarimetric SAR Interferometry

Polarimetric SAR interferometry (PolInSAR) is a well known technique that can be applied to inversion of vegetation parameters. In this paper, a two-layer coherent scattering model composed of a random volume over the ground is established firstly to describe the vegetation parameters, and then the polarization and interference are unified by defining a complex interferometric coherence which can be gained through the model. Finally the measured SAR data is substituted into the expression of the complex interferometric coherence to come true the inversion of vegetation parameters. In the process of the inversion of vegetation parameters, three-stage method is used. By employing the method, ground topography can be received accurately and other vegetation parameters such as vegetation height and mean extinction coefficient also can be estimated. However, the random model is based on the assumption that volume interferometric coherence is independent of polarization. Under normal circumstances, the propagation of the electromagnetic waves is anisotropic because the extinction coefficients are highly polarization dependent, namely, that volume interferometric coherence is dependent of polarization, so a new vegetation model composed of an oriented volume over the ground needs to be created. For the inversion of the oriented model, three-stage method is still used and the inversion procedure is similar with the random model. The difference between them is the interferometric coherence of random is a line inside the unit circle of the complex coherence plane, while oriented is a triangular region. The simulation results demonstrated that an accurate inversion of the vegetation parameters is still possible.