Study On The Application Of Nonlinear Tracking Filter In InSAR Phase Unwrapping

Synthetic Aperture Radar Interferometry(InSAR)technology has the advantages of all-day,all-weather,high efficiency,high precision and large area.It has been widely used in creating digital elevation models(DEM)for topographic mapping and extracting deformation field for surface deformation monitoring.However,in practical application,many key technologies of InSAR are not mature enough,and phase unwrapping,as one of the key technologies of InSAR,needs further research and exploration.In this paper,we study two kinds of phase unwrapping methods,quality-guided path following method and least square method.Based on Kalman filter model,three Kalman filter phase unwrapping methods,EKFPU,UKFPU and CKFPU,are studied.The disadvantages of the above methods are analyzed.For example,the quality-guided path following method needs to follow some prior conditions and depends on the quality map,the least square method based on FFT is easy to lead to error transfer,and the EKFPU,UKFPU and CKFPU algorithms can not meet the requirements of many complex tracking applications.The innovation of this paper lies in,based on SCKF algorithm,a phase unwrapping method,called square-root cubature Kalman filter phase unwrapping(SCKFPU)is proposed.This method is used to unwrap the phase from high reliable pixels to low reliable pixels by the designed phase quality estimation function and the optimal path following strategy.The main research work and contributions of this paper are summarized as follows:(1)The factors that affect the phase unwrapping are analyzed: under-sampling and noise.The influence of the number of sampling points and different degree of noise on phase unwrapping is analyzed by simulation data.(2)The quality-guided path following method and least square method based on FFT are studied,their principles and concrete implementation steps are analyzed in detail,the advantages and disadvantages of these two algorithms are analyzed according to the simulation data and the measured data.(3)EKFPU,UKFPU and CKFPU methods are studied.In the local frequency estimation,use the two-dimensional Chirp-z transform to improve the precision.Kalman filter phase unwrapping methods was validated the feasibility and effectiveness of reconciliation by the simulation data.Use the real InSAR data experiment,through the three phase unwrapping methods,comprehensive evaluation of the performance of these methods.(4)Aiming at the shortcomings of previous phase unwrapping methods,we put forward the SCKFPU algorithm.The principle and implementation steps of the algorithm are described in detail,the phase estimation function and the optimal path following strategy are designed to optimize the unwrapping path.Simulation results based on the simulation data,true InSAR data,and measured(real)InSAR data of the experimental results prove that the method can achieve better performance compared with other existing phase unwrapping methods.