Research And Implementation Of Airborne SAR Image Geocoding

Synthetic Aperture Radar(SAR)is an earth observation system that uses equivalent synthetic aperture theory to obtain high-resolution SAR images.It can be carried on satellite platforms which is called spaceborne SAR and aircraft platforms which is called airborne SAR.Since the airborne SAR is capable of all-day observation and is suitable for harsh observation environments,and that it can achieve high image resolution.Airborne SAR images are widely used in crop yield estimation,disaster monitoring and rescue,topographic mapping,military reconnaissance and other fields.Due to its slant range and side-view imaging characteristics and the non-ideal motion during the data collecting,the airborne SAR image will suffer from geometric distortion which affects the identification and geometric positioning of the airborne SAR image.Therefore,it is necessary for airborne SAR images to geocode.The airborne SAR image geocoding is a post-processing process of airborne SAR images,which outputs SAR image information in the form of a fixed grid of the earth(map image)that is easy for people to understand.Therefore,geocoding of airborneSAR images has great application prospects and research value.In this thesis,it took the airborne SAR image as the research object Starting from the processing flow of geocoding,this thesis focuses on the geometricpositioning in the airborne SAR images geocoding process,and discusses and analyzes the factors affecting the accuracy of geocoding images.Through the analysisand verification experiments and the processing data of the Weihe Bridge in Weinan City,Shanxi Province,the feasibility and effectiveness of the proposed algorithm and the correctness of the error model are verified The main research contents are as follows:1.Introduction to the necessity analysis and processing of airborne SAR images geocoding.Firstly,the obtaining method of the non-geocoding airborne SAR image is introduced.Then the necessity of airborne SAR image geocoding is analyzed,and finally the processing flow of airborne SAR image is introduced.2.Introduction to the geometric positioning technology in the airborne SAR image geocoding process.The airborne SAR image geometric positioning methods are classified and compared and then the range-doppler geometric positioning method which is the most widely used is introduced.By comparison,this thesis uses the least squares method as the solution of the range-doppler positioning method.3.Implementation of the airborne SAR images geocoding.Based on the processing of real data in the Weihe Bridge area,the implementation of traditional airborne S AR image geocoding is introduced,and then an improved geocoding algorithm based on space-variant polynomial and a geocoding algorithm based on reverse positioning are proposed.The errors of monitoring points of three geocoding algorithm are compared and analyzed.4.Analysis of the influence factors in the range-doppler positioning process and the error modeling.Experiments are carried out to verify the correctness of the error model which can guide the design of SAR system parameters.