An Improved Three-Stage Inversion Algorithm in Forest Height Estimation Using Single-Baseline Polarimetric SAR Interferometry Data

This letter provides an advanced method to improve the result for three-stage inversion algorithm, using polarimetric synthetic aperture radar interferometry (PolInSAR) technique based on the random volume over ground model. In the conventional three-stage method, the ground phase, extinction coefficient, and volume layer height are estimated in a geometrical way without the need for a prior information or separate reference digital elevation model. The extinction and volume height estimation is done in the third stage by searching in the 2-D area. In the proposed algorithm, defining a new geometrical index, according to signal penetration in the forest, imposes a limited range for the extinction coefficient. The new index, as an axillary data, helps make searching limited to a reasonable 2-D area. The proposed algorithm was applied on L-band E-SAR single-baseline single-frequency PolInSAR data. As a result of applying this restriction in the extinction range, a 2.5-m improvement was observed in the RMSE of the proposed algorithm compared with that of the conventional three-stage method.