Study On The Influence Of Spacedorne SAR Orbital Data On Image Geolocation

With the rapid development of social economy, synthetic aperture radar (SAR) applications are widely used in all areas of society. During the past decades, a variety of radar satellites have been launched, which provide rich SAR data sources for different applications. However, due to certain technical limitations, the orbital data provided by some satellites are not so accurate, which brings so many problems to the subsequent data processing.In view of the above questions, in this paper, based on the imaging equation of SAR imagery, the impact of satellite orbital data on the geolocation accuracy of SAR image is studied in detail. Especially, the images of Radarsat-2 and TerraSAR-X are analyzed.The main research contents are as follows:1) The determination of orbital data fitting method. The cubic polynomial model is selected to fit satellite orbit through the fitting accuracy contrast Kepler orbital method and cubic polynomial method.2) Derivate the imaging equation and introducing geolocation. On the basis of cubic polynomial orbital model, the SAR imaging equations are derived in detail. In addition, the error equation of SAR geolocation is given. Two direct geolocation methods are introduced based on the imaging equation, namely the Newton iterative method and the slant coordinate transformation method. The derivations of both methods are given, together with the flowchart. Meanwhile, the indirect geolocation method based on the Newton iterative algorithm and SAR imaging equation model is provided. Then, taking Radarsat-2 and the TerraSAR-X images as experiment data, the indirect and direct geolocation methods of SAR images are tested combining Some corner reflectors were deployed in synchronization with SAR image acquisitions to collect ground control points.3) Analysising the orbit data impacted to geolocation. Once more, because the Radarsat-2 images and TerraSAR-X images accuracy of indirect geolocation are very similar, the article has conducted a further theoretical derivation and give the derivative of the satellite (XS,YS,ZS) with respect to the ground point(XT,YT,ZT)and the derivative of the orbit position vector(XS,YS,ZS)with respect to the slant range R and time t to determine the impact of orbit vector to the direct and indirect geolocation. Finally, different errors are added into the three components of the orbit vector of Radarsat-2 data and TerraS AR-X data, and a series of experiments of direct and indirect geolocation are performed on the irrupted data.