A Study Of 3D Location Of Airborne Repeat Pass InSAR

Synthetic Aperture Radar(SAR)is a kind of observation system which is different with traditional photic observation system.SAR can provide full-time,full-weather,high penetration and high resolution active observation for targets.Comparing with space borne SAR,airborne SAR is flexible and easy to imply.Airborne SAR also has the ability of real-time imaging.The advantages of airborne SAR make it provide testing for space borne SAR.Interferometric Synthetic Aperture Radar(InSAR)could generate the three dimensional terrain maps by the differential interference contrast of two complex images.InSAR inherits the advantages of SAR,but dual antenna system usually is limited by the sort of airborne platform.Repeat Pass Interferometric Synthetic Aperture Radar(RP-InSAR)breaks the limitation of dual antenna system and plays an irreplaceable role in topography surveying and deformation monitoring.Especially,due to different surveying time in Surface micro-deformation measurement and surface activity monitoring,repeat pass interferometric is irreplaceable.In order to obtain accurate ground elevation information,the two flight trajectories of RP-SAR must keep close to a specific spatial baseline.The flight trajectory is often deviated from the ideal track due to the limitation of the precision of the navigation system.In measurement,the influence of flight instable altitude and attitude will result in position shift and attitude changing of the aircraft-carrier.Limited by the precision of inertial navigation system,antenna phase center location and radar beam pointing still have some errors.Since the two flight tracks does not coincide exactly in the observation of InSAR,there are still obvious irregular relative deformations between two interference complex images.Even after motion compensation,the corresponding ground resolution units of the same image element are inconsistent.Especially under the long baseline conditions,from the SAR image close to the far-end,the size of the inconsistency program gradually increased.The lost registration of interference complex images is very serious,and the coherence is greatly reduced.The difficulties of obtain high-precision DEM in late interference processing causes difficulties to carry out three-dimensional positioning.In order to achieve the three-dimensional positioning of RP-InSAR,we studied the coordinate system related to SAR images and the transformation relationship between the coordinate systems,and deduced analytic imaging model and threedimensional positioning model of RP-InSAR.A high precision positioning and interference processing method based on RD imaging model is proposed.The method used RD image model to solve correction values of the flight height and initial range,which used POS data and ground control points data.The method is able to achieve the high accuracy relative positioning of corresponding points on InSAR images and he high accuracy InSAR image registration.High accuracy DEM generated after interference processing,as a result the three dimensional location of corresponding points can be determined.The experimental data of this paper is the RP-InSAR image pairs obtained in october 2014,Lingshui area,Hainan Province.The important reasons that affect the accuracy of SAR image registration are the incomplete coincidence of flight trajectories and the low precision of POS data.The reasons causes difficulties of pixel location.The experimental result shows that using RD imaging model to correct the imaging parameters could improve the positioning accuracy of three dimensional locations.In large image areas,this method can effectively obtain high position precision that the traditional method cannot obtain.The method solves the problem of threedimensional positioning of the airborne RP-InSAR.