Correction Of Atmospheric Water Vapour Effects On Corner Reflector InSAR And Ground Subsidence Monitoring

As well known,temporal and geometric decorrelation represents the most important limiting factors in synthetic aperture radar interferometry(InSAR) Due to this fact,analyses of low coherence areas(e.g.,forested and vegetated areas)with conventional InSAR methodologies cannot be performed successfully.Even the application of advanced InSAR algorithms,such as the permanent scatterer(PS)technique,may prove to be ineffective wherever the density of stable radar targets(i.e.,the PS)is extremely low.In order to overcome this limitation,the usage of artificial reflectors can be very promising.In this paper,at first we give the basic theory and algorithm-processing flow chart of InSAR and DInSAR.Then,the deformation monitoring theories of CRInSAR were introduced,especially the algorithm of CRInSAR presented by Xia Y.of Germany GFZ.Second,we analyzed structure and composition of the atmosphere.Based on the differences of effects,the layered structure of the atmosphere is redefined as tropospheric and ionospheric effects.Because the ionospheric effects are very small in CRInSAR and the majority of atmosphere effects are from tropospheric,we analyzed the tropospheric effects to CRInSAR and compare atmospheric correction models.At last,the method and process of using CGPS data to correct atmospheric effects are analyzed.In the third part,we applied the Least Squares Ambiguity Decorrelation Adjustment(LAMBDA)method which has been applied in GPS ambiguities resolution to solve the problem of phase unwrapping,in order to solve the phase unwrapping problem of CR-InSAR.Real data is used to test the unwrapping method and reliable results are achieved compared with other method.Then the new CRInSAR algorithm was proposed.Based on the assumption that the deformation includes the linear and the periodic parts,we modeled the deformation and solved it.At last,we investigate and compare the process and results achieved in three test fields in Hong Kong in order to demonstrate some algorisms in CRInSAR and to estimate the reliability and precision of the method in slop movement and ground deformation monitoring.We used the data from CGPS observations to correct the interferometric phases for the temporal atmospheric inhomogeneity first.Then we used the standard DInSAR and the Corner Reflectors technique(CR).The results of deformation of the CR point extracted from the DInSAR are similar with solutions from CRInSAR technique.The comparison of the results demonstrates that the Algorithms of CRInSAR are reliable and precise.