Topography and Tree Height Estimation Based on the Best Normal Matrix Approximation for PolInSAR Coherence Region

The inversion of topography and tree height in forest area is one of the most important applications in the Polarimetric SAR Interferometry (PolInSAR). In this paper, the coherent region of the PolInSAR data is modeled and the best normal matrix is used to approximate the cross correlation matrix, further, the whitened interferometric cross-correlation matrix is obtained. The coherence region of the whitened interferometric cross-correlation matrix is a straight line. Two arbitrary coherences obtained under two different polarization states can be applied to fitting a straight line. Based on the fitting line, the topographical phase can be estimated successfully. Referring to the relationship between the volume scattering and the tree height, look-up table method is used to search the correct tree height. The proposed method can avoid the complex steps of the traditional method, which needs to solve all the coherences under different polarization states to obtain the edge of the coherent region. The proposed method simplifies the inversion procedure and improves the efficiency of inversion, meanwhile, achieves the correct topography as well as the tree height. Finally, the simulation data are applied to validating the validity and reliability of the proposed method.