Study On Phase Unwrapping Method Of L-band Differential Interferometric SAR

Interferaperture Radar(In SAR)technology has all-weather and all-sky characteristics;It has been widely used in producing high-precision Digital Elevation Model(DEM)and monitoring surface deformation.The accuracy of In SAR data processing steps will directly affect the accuracy and reliability of the final In SAR products.As one of the most critical steps in the whole data processing,phase unwinding will directly determine the accuracy of the final DEM.So phase unwinding has always been a hot and difficult point in In SAR data processing.In this paper,a single baseline phase unwinding method suitable for high noise region is studied,and the post-processing of error points in the multi-baseline phase unwinding method is studied.The main research contents are as follows:(1)Conduct an in-depth study on In SAR’s method of producing high-precision DEM,and introduce each step of In SAR data processing process in detail.The main error sources in the whole data processing process are analyzed,which provides a theoretical basis for the following phase unwinding method research.(2)Study on MCF phase unwrapping method based on local frequency correction.In order to solve the problem of poor robustness of MCF noise,a phase unwinding method of MCF based on local frequency correction is proposed.The method first Amended the frequency estimates obtained by the Amended Matrix Pencil Model(AMPM)to make the obtained phase gradients more accurate,and then amended phase gradients were incorporated into the MCF phase unwinding model.By comparing the simulation data experiment with the real data experiment such as L-SAR,the improved MCF phase unwrapping algorithm has higher unwrapping accuracy and noise robustness,but also has the ability to take into account the terrain,and has a certain improvement in the unwrapping efficiency.(3)Research on improved multi-baseline elevation reconstruction method based on maximum likelihood estimation.In view of the serious burr in the result of Maximum Likelihood(ML)elevation reconstruction algorithm,a ML elevation reconstruction method combined with AMPM algorithm was proposed.Firstly,the residual handicap of multiple interferogram is combined with the error points of the initial ML elevation reconstruction results to obtain the elevation error points that need post-processing.Then,AMPM algorithm is used to obtain the phase gradient between the elevation error points and the surrounding good points.Finally,combined with the height fuzzy number,the altitude error points are post-processed by the surrounding good points.By comparing the simulation data experiment with the real data experiment,the improved ML algorithm has higher unwrapping accuracy and noise robustness while ensuring the unwrapping efficiency.