Application Of Spaceborne Insar Technique In Monitroing The Land Subsidence

Land subsidence is a phenomenon that the earth surface is being deformation in vertical direction under the natural or human factors. There are many cities that have been troubled by the land subsidence at different degree in China. The land subsidence has become one of major geological disasters, which restricts sustainable development of the regional environment and social economy.Spaceborne differential radar interferometry(D-InSAR) technique is a new earth observation tehchnique developed in 1990s. It can measure minute earth deformation, such as earthquake, volcano dynamics, glacier movements, land subsidence and landslide. The precision can be achieved at the centimeter level, even the millimeter level.Compared with the conventional techniques to monitor the land subsidence, D-InSAR technique has the advantages with large cover, rapid, accurate, low cost. However, a full operational capability has not been achieved yet due to atmospheric disturbances, temporal decorrelation and baseline decorrelation phenomena. And the utility data processing method needs further research.This paper emphasizes on analyzing the basic principle and key methodologies, studying the utility methods of data processing, carrying out some case tests of D-InSAR technique in detail. It also deeply studies different D-InSAR data processing methods. It mostly includes the contents as follows.(1)It studied the basic principle and the data processing method of D-InSAR technique. Then it analyzes the error sources, which influence the measuring precision of D-InSAR. It sums up the methods to select the interferometric SAR data.(2) It studied the utility method of InSAR data co-registration. And it put forward to a new utility method based on the DEOS precise orbital data and interpolating the coherence matrix. We can get the initial offset of central pixel of master image using the DEOS precise orbital data. It can also save the performing time of program through interpolating the coherence matrix not over sampling the SAR images. The test proves that this method can accomplish the sub-pixel co-registration with high precision.(3) It studied the utility method of baseline estimation. And it put forward a refine method. The method is to estimate the initial baseline based on the DEOS precise orbital data and co-registration parameters. Then it is to revise the baseline based on the high-precision DEM. Then it analyzes the influence of DEM error for the baseline estimation. We carry out baseline estimation test using ERS-1/2 data. It is proved that it is a utility method of baseline estimation based on the DEOS precise orbital data and SRTM DEM in plain areas.(4) We successfully get the Bam co-seismic deformation fields using the 3-pass D-InSAR technique and ENVISAT ASAR data. Then we interpret the deformation fields in detail. It generates the profiles and isoline map of land subsidence for facilitating to interpret the deformation fields. It summed up the area of land subsidence. We detect the location, distribution and area of the serious destruction region caused by the Bam earthquake using the coherence maps. This method compares the coherence maps of pre-, co-, post-seismic. Then it sums up the applications of coherence map in InSAR data processing.(5) It studies the influence of atmospheric effect for the InSAR measuring. It gets the atmospheric delay phases in InSAR measurement through 2-pass D-InSAR technique and Interferometric Point Targets Analysis technique tests. Then it explores the methods of correcting atmospheric effect in InSAR measurement.(6) It studies Interferometric point targets analysis (IPTA) technique taking Suzhou region for example. Firstly, it analyzes the model of phase analysis and studies the methods of data processing of IPTA in detail. It forms the utility flowchart of data processing. It focuses on the selection of reference image and point targets. It sums up 3 principles of selecting the reference images. Then it selects the point targets using the double thresholds method. IPTA test exploits the temporal and spatial characteristics of interferometric signatures collected from point targets from 38 ERS-1/2 data. It accurately gets surface deformation histories and atmospheric path delays in Suzhou region.