Research On Calibration Of Atmospheric Delay In High Resolution PSI By Integrating CORS GPS Data

Land subsidence is an irreversible regional geological disaster with slow accumulation,if long-term effects,not only the city buildings,flood control system,linear underground pipelines,linear urban infrastructure such as subway and railway,but also people's life and industrial production,will be under threat.Therefore,it is urgent and meaningful to carry on the timely and effective monitoring for urban land subsidence,to study the subsidence mechanism,to grasp the distribution characteristics and temporal and spatial variation and to implement effective control and prevention for urban land subsidence.In recent years,permanent scatterer InSAR(PSI)developed from differential interferometric synthetic aperture radar(DInSAR)inherites the deformation monitoring advantages with wide coverage and high spatial resolution of DInSAR,and overcomes the temporal decorrelation.At the same time,through separating atmospheric delay partially,it can reduce the influence of the atmospheric delay on PSI deformation monitoring,and improve the accuracy of deformation calculation.Also,it can invert the temporal and spatial evolution of surface deformation.In addition,with the successful launch of the high resolution satellites e.g.,TerraSAR-X,COSMO-SkyMed,the PSI technology based on high resolution SAR images has been developed rapidly and has become one of the important technical means for slow surface deformation monitoring.Although high resolution PSI has many advantages in deformation monitoring,it inhibites a certain degree of atmospheric delay by using the method of time domain low pass filter,which is based on the temporal and spatial correlation of atmospheric delay.However,atmospheric delay is still an important error source of high resolution PSI for that filtering can not accurately estimate and eliminate atmospheric delay,.In order to improve the atmospheric delay correction precision of the high resolution PSI,and to improve the precision and reliability of high resolution PSI deformation monitoring,the project that joint CORS data for high resolution PSI atmospheric delay correction and take ChengDu as the study area was proposed in this thesis.The specific research work mainly includes the following contents:(1)In view of the limitation of the accuracy of high resolution PSI atmospheric delay correction through filtering,this paper proposes combining with advantages of CORS data to correcte high resolution PSI atmospheric delay with the analysis of the possibility of using CORS data for high resolution PSI atmospheric delay correction,and the analysis of difference of atmospheric delay between GPS system and SAR system.(2)Based on the existing problems of conventional InSAR atmospheric delay correction with the fusion of GPS and the factors that cause the difference between atmospheric delay of GPS system and SAR system,the atmospheric delay deviation model for CORS data and high resolution PSI were established.Then,based on the atmospheric delay deviation model,the corrected high resolution PSI atmospheric delay was calculated with the high precision CORS data atmospheric delay parameters.(3)A new high resolution PSI neighborhood differential interferometric phase model is proposed based on the existing PSI neighborhood differential interference phase model.In this model,the atmospheric delay is a known quantity that corrected by CORS data.And based on this model,deformation phase of each PS point are solved.Among them,the linear defonnation rate is still solved by the least squares method,while the nonlinear deformation phase is obtained only by low pass filtering on the residual phase in the spatial domain;(4)The TerraSAR-X images covering Chengdu urban area and Sichuan CORS network data from 2010 to 2015 are used for high resolution PSI deformation monitoring.The deformation results included the method of correcting high resolution PSI atmospheric delay by spatial filtering and correcting high resolution PSI atmospheric delay by the atmospheric delay deviation model and new high resolution PSI neighborhood differential interferometric phase model that proposed in this paper.The deformation of the two methods calculation results were compared and analyzed,which shows that the results of deformation monitoring based on the method proposed in this paper are more reasonable and reliable,and are more consistent with the actual reports and the actual construction.Theoretical analysis and experimental studies have shown that the method proposed in this paper can effectively correct high resolution PSI atmospheric delay and is advantageous than the conventional filtering method.In addition,the paper also analyzes the distribution characteristics and the temporal regularity of the deformation in Chengdu area,predicts the dynamic load of the underground engineering construction,the dynamic load applied by the high-rise buildings to the foundation and the change of groundwater environment by the large amount of groundwater exploitation in the process of urban construction may be the main reasons leading to Chengdu land subsidence.