Airborne SAR/InSAR Motion Compensation And Baseline Correction Technology With Its Engineering Application

Synthetic aperture radar(SAR)and interferometric synthetic aperture radar(In SAR)are widely used in military and civil fields because of their all day and all-weather characteristics.Airborne SAR / In SAR plays an indispensable role in deformation monitoring,hidden target recognition,rapid mapping and other aspects because of its unique characteristics.Nowadays,with the diversification of application requirements and the complexity of Surveying and mapping terrain,airborne SAR / In SAR technology is gradually developing in the direction of high precision,intelligence and high efficiency.With the emergence of a large number of airborne SAR / In SAR systems at home and abroad and the progress of a large number of echo recording work,engineering implementation and high-precision processing are particularly important.Aiming at the current development trend and existing problems of airborne SAR / In SAR,this paper studies the high-precision motion compensation and In SAR baseline error correction technology for different data,and carries out engineering application.The specific work includes the following contents:1.A motion compensation method for Airborne SAR imaging based on POS(position and orientation system)measurement data is studied.This method combines the requirements of In SAR imaging and ideal SAR imaging geometric model,and uses the measured position and attitude information of antenna phase center(APC)and the auxiliary digital elevation model(DEM),For high-frequency band and narrow beam data,two-stage motion compensation mechanism is adopted,while for low-frequency band,wide beam and complex observation scene data,three-stage motion compensation mechanism is adopted.2.Due to the low measurement accuracy of inertial navigation data,the motion compensation is not complete and the SAR image is defocused.However,the interference phase will be destroyed when the SAR image is processed directly with autofocus algorithm.Therefore,a phase preserving autofocus processing method based on error transfer is proposed.The specific principle is that for the short baseline airborne dual antenna In SAR system,the motion error difference of the master and the slave antennas is analyzed.If the error difference meets certain conditions in different bands,the phase error function estimated by the master image autofocus processing can be used to compensate the master and the slave SAR images at the same time to improve the focusing performance of the master and the slave images.This processing method does not destroy the interference phase,but also improves the coherence of the master and the slave images due to the improvement of focusing.The actual data processing results of the airborne In SAR prove the correctness and effectiveness of the algorithm.3.The interference baseline is one of the important parameters in In SAR processing.The baseline error will seriously affect the interference phase,causing the interference phase to fluctuate and bend in the azimuth direction,and then affect the accuracy of the elevation.Aiming at the limitation of the DEM auxiliary algorithm to regard the baseline as a constant value,the azimuth coincident block method is used to improve it,so that it can estimate the time-varying baseline error and conform to the reality.At the same time,combining the advantages of the multiple squint algorithm and the DEM auxiliary algorithm,a joint processing flow is studied.The main idea is to divide the time-varying baseline error into two parts: high-order term error,constant and linear term error,and use multiple squint and DEM auxiliary algorithms to estimate them respectively.This method not only improves the accuracy of estimation,but also reduces the accuracy requirements for auxiliary DEM data.The actual data processing result of the airborne In SAR proves the correctness and effectiveness of the improved algorithm and the joint processing procedure.4.Aiming at the requirements and characteristics of airborne SAR imaging and time-varying baseline error uncontrolled estimation of In SAR,the airborne SAR imaging and time-varying baseline error correction software is designed from data input / output interface,parameter setting interface,diversified selection,intelligent application,etc.It is verified by airborne measured data,and the results of engineering application are given.