Phase Error Model Of Spaceborne Distributed InSAR On Terrain Surveying And Mapping

Spaceborne distributed synthetic aperture radar Interferometry(SAR,InSAR)technology is a new type of earth observation technology that has springing up in recent years.It is implemented with synthetic aperture radar onboard the formation flying satellites,using synthetic aperture technology and pulse compression technology based on the SAR geometric image model.The two SAR antenna obtained two scenes which are single look complex images.By processing these images,surface elevation information are obtained and the corresponding region of digital elevation model(DEM)are established.InSAR Technology has the advantages of high accuracy and all-weather imaging because of its microwave imaging characteristics.It can efficiently build seamless DEM in large area.First,this paper studies the measurement principle of the distributed spaceborne InSAR system,the error of InSAR mapping,and an error model is established.Then,the source of the phase error in the InSAR terrain surveying and mapping is studied,and the relationship between the phase error and the phase gradient is modeled and analyzed.Finally,the impact of the InSAR spatio-temporal baseline on the height measurement accuracy is demonstrated experimentally.The research in each chapter is arranged as follows:The first chapter expounds the classification and current situation of the development of spaceborne InSAR system.It is pointed out that the InSAR system which has one antenna has long revisit period that leads to time decoherence.The single pass system with two antennas can accurately measure the spatial baseline,there is almost no time decoherence.Then,the classification and development status of the spaceborne distributed InSAR system are studied,and the application status of the Tan DEM-X system is also discussed.In the end,the error of the spaceborne distributed InSAR system is summarized.In the second chapter,we study the error categories in the InSAR terrain surveying and mapping,establish the error model for the height measurement accuracy,and analyze the characteristics of the errors.First,the error of topographic survey is divided into the absolute error and relative error,absolute error includs satellite orbit error,satellite velocity error,oblique distance measurement error,baseline measurement error and phase offset,the relative error almost include all kinds of decoherence sources: thermal noise decorrelation,baseline decorrelation,quantitative correlation,ambiguity decorrelation,volume scattering decorrelation,temporal decorrelation.Then,the magnitude and propagation characteristics of each error in InSAR topographic mapping are studied.Finally,combined with the InSAR altimeter principle,the influence models of the main observation errors on the altitude accuracy of the spaceborne distributed InSAR system are derived,and the influence of errors on the height accuracy can be quantitatively calculated through the model.Finally,combined with the InSAR altimeter principle,the influence models of the main observation errors on the altitude accuracy of the spaceborne distributed InSAR system are derived,and the influence of errors on the height accuracy can be quantitatively calculated through the model.In the third chapter,the sources and characteristics of interference phase errors are studied,and the phase unwrapping method is summarized.The relationship between the phase unwrapping accuracy and the phase gradient is studied through the simulation experiment.First,the interferometric phase error is divided into the hardware system error,the model error and the processing error.Then,the phase unwrapping methods are briefly introduced,and the appropriate unwrapping method is selected through experimental analysis to help modeling the relationship between phase gradient and phase unwrapping accuracy.Finally,the mathematical model of the relationship between the phase unwrapping accuracy and the phase unwrapping gradient is established through the simulation experiment.In the fourth chapter,the influence of space-time baseline on the height measurement accuracy of spaceborne distributed InSAR system is studied.We quantitatively analyze the effect of spatio-temporal baseline in InSAR topographic mapping,and analyze 40 Terra SAR-X images to summarize the influence of spatio-temporal baseline on coherence and height measurement accuracy.