Research On Vegetation Parameters Inversion Method Of Single/Multi-baseline PolInSAR

With the increasing requirement of grasping the information of the observed targets in the field of space remote sensing,Polarimetric Interferometric Synthetic Aperture Radar(PolInSAR)emerges as the times require.PolInSAR can acquire the fine physical characteristics and spatial elevation information of the target simultaneously.Therefore,the use of PolInSAR for three-dimensional spatial geographic mapping has broad application prospects.PolInSAR signal processing technology can well separate the phase centers of different scattering mechanisms,and has high estimation accuracy for vegetation canopy phase and surface phase under vegetation.Therefore,the inversion technology of vegetation parameters in PolInSAR research field provides help for forest resource control,geographic exploration,environmental detection and other applications.Based on the basic theory of classical single/multi-baseline PolInSAR parameters inversion,this paper deeply studies the shortcomings of classical vegetation parameters inversion algorithm under model mismatch,and proposes effective improvement methods.The main contents and research work are as follows:(1)The polarization scattering vectors and polarization coherence coefficients related to PolInSAR signal processing are studied,including their expression forms and physical meanings.Three scattering mechanisms under Pauli decomposition are analyzed,and the scattering mechanisms of different objects with different dominance are verified by the measured data.Then the optimization method of polarization coherence coefficient is analyzed,and the simulation data prove that the method can improve coherence and separate different scattering mechanisms.(2)The classical PolInSAR vegetation parameters inversion model and method are studied.Firstly,the structure of RVoG two-layer vegetation model and the expression of polarization coherence under this model are studied.Then two methods of vegetation parameters inversion based on RVoG model are studied: direct altitude difference method and three-stage analytic geometry method.Then two methods of vegetation parameters inversion based on RVoG model are studied: direct altitude difference method and three-stage analytic geometry method.The validity of these two methods is verified by inversion of vegetation parameters for simulation data.The inaccuracy of phase center estimation of surface in direct altitude difference method and the ambiguity of terrain amplitude ratio in three-stage analytic geometry method are also analyzed.(3)Two improved single baseline PolInSAR vegetation parameters inversion algorithms are proposed.Firstly,for the dense vegetation scene with terrain gradient,the problems of RVoG model mismatch,Polarization Oriented Angle(POA)migration and inaccurate estimation of polarization coherence matrix caused by terrain gradient are studied.A vegetation parameters inversion algorithm based on topographic effect compensation is proposed.The simulation data verify that it has higher inversion accuracy than the existing methods.Scattering mechanism of sparse vegetation canopy is studied in sloping sparse vegetation scenario.At this time,even scattering dominates vegetation canopy.The phenomenon that interference phase of vegetation canopy deviates from the real position of vegetation caused by even scattering dominance is analyzed.At this time,the independent and identical distribution characteristics of polarization coherence matrix estimation samples are reduced.Therefore,a vegetation parameters based on sample selection is proposed.The numerical inversion algorithm has higher inversion accuracy than the existing methods through simulation data.(4)An improved multi-baseline PolInSAR vegetation parameters inversion algorithm is proposed.Aiming at the problem of ambiguity of terrain amplitude ratio in single baseline parameters inversion algorithm,a multi-baseline joint method based on optimal linear fitting is proposed to solve the ambiguity of terrain amplitude ratio,which avoids the ambiguity of terrain amplitude ratio in single baseline vegetation parameters inversion algorithm,and the effectiveness of the algorithm is verified by simulation data.