Research On Distributed InSAR Baseline Determination Method Combining The Information Of GNSS And Ground Control Point

Distributed InSAR is one of the most potential radar systems for ground elevation measurement and can effectively avoid temporal decorrelation impact.Compared with other systems,it is less restricted by satellite platform,when its accuracy of elevation measurement is better and its baseline can be freely controlled.Therefore,it will be the mainstream in the future development of spaceborne InSAR technology.But since the elevation measurement accuracy of distributed InSAR system is largely depended on the accuracy of inter-satellite baseline,high-precision baseline determination has become the premise and key of the distributed InSAR mission.this paper,whose research background is InSAR earth observation technology,focuses on the baseline determination method combined with ground control point and GNSS.The main work of this paper includes three aspects:First,two kinds of baseline determination methods are studied.We start with the research of the inter-satellite baseline estimation method.We deduce the mathematical models of three-point method and five-point method,which belong to the ground control points methods,analyzing the advantages and disadvantages of two methods,explaining the drawbacks of ground control point methods.Then,we study the baseline estimation method based on the information of GNSS observation.We introduce the technological process and the errors of GNSS baseline estimation method,and carry out the simulation experiment of the the errors' impacts,in which the accuracies of GNSS baseline estimation products are analyzed.The results show that,under the impacts of all the errors,there are 9.90 mm of fixed error and 0.76mm(1 sigma)of random error in the baseline products,in which fixed error is the main contradiction affecting the accuracy of the baseline.Second,the baseline determination method combined with ground control point and GNSS is studied.Firstly,based on theoretical analysis and on-orbit experiment,we find the characteristic of baseline bias which is stable in multi-orbit.Then,we introduce the main flow of the baseline determination method combined with ground control point and GNSS,and deduce the mathematical model of baseline bias calibration.After analyzing the characteristics and the sources of the new errors introduced by baseline bias calibration method,we simulate the impacts of errors to analyze the accuracy of calibration method.The experimental results indicate that slant range distance error is the most influential error among all kinds of errors.Third,the improved method for baseline calibration to suppress the impact of slant range distance error is studied.First of all,we study the impact mechanism of slant range distance error to the error of InSAR elevation measurement,deriving the relationship between the slant range distance error and the component of baseline bias vector parallel to the line of sight.Because of the constant characteristic of slant range distance error in the process of single interference observation,a new method is proposed to suppress the impact of slant range distance error with calculating partial derivative,through which we establish the mathematical model to calibrate the baseline bias with the observation data under two incident angles.At last,we use simulation experiment to verify the correctness of the improved baseline bias calibration method to suppress the impact of slant range distance error,and evaluate the accuracy of the improved method under the influence of comprehensive error.The results of evaluation show that the improved method can suppress the impact of slant range distance error effectively.