The Research Of The Doppler Parameters Calculation Method In Airborne SAR Imaging

For airborne SAR, when get good quality echo data and the GPS positioning and IMU data of the aircraft platform, either InSAR interference measuring or use SAR image mapping must proceed focused imaging first about echo data.In order to perform the radar image terrain, geophysics interpretation, request radar images focused imaging radiation astigmation small, image boundary clear, can accurate reading, and in process of electromagnetic focused imaging of SAR, Estimate doppler parameters accurately, correct distance migration and motion compensation strictly, can focus at a high level, SAR high quality focused imaging is important to produces high-precision DEM data and orthophotomap and improve production efficiency, because when Airborne SAR obtain echo data, it is not easy to achieve the requirements of ideal flying conditions as-constant speed, equal altitude. Along the designed air route, positive side-looking". In this case, estimate doppler parameters accurately appears especially important. there are three main aspects about airborne SAR focused imaging:(1) Doppler parameters calculation:Doppler center frequency and doppler adjustable frequency are important parameters in structure reference function in SAR focused imaging.(2) Correct distance migration and motion compensation:Only to proceeding these two corrections precisly, the precisly range direction and azimuth direction matched filtering can realize.(3) Range direction and azimuth direction matched filtering:Different algorithms have significantly influence on matched filtering precision and the calculation efficiency.In this paper doing the following aspects of work according to doppler parameters estimation: Firstly, based on this experiment research deduce strict geometric model calculation formula.mainly to use airborne SAR echo data and carrier aircraft POS data of Chinese surveying and mapping science research institute, to verify the accuracy of the model. In addition, is to use ground control points and carrier aircraft POS data to verify this model method.Secondly, ~Clutter filter" calculate doppler center frequency. In the condition of high time bandwidth product in azimuth direction of SAR, make the doppler frequency and the position that along the trajectory lock together~self-focusing" calculation doppler adjustable frequency. Azimuth subaperture related to~self-focusing" based on the orientation time or location between the locking relationship of doppler frequency.Again, the doppler parameters of global estimation. Including Space change detection, quality control, geometry model, global fitting.Finally, the overall adjustment of doppler parameters. adjustment of doppler parameters that Through geometrical model calculation doppler parameters and through echo data calculation doppler parameters.This paper based on the research of doppler parameters, puts forward geometric model method and global estimation, mainly solved the problem that how to use the aircraft POS data to precisely figure out doppler parameters, This parameter data are available to provide accurate imaging.