Research And Application Of An Algorithm For CR And PS D-InSAR Joint Calculation

Conventional InSAR (SAR Interferometry) technology has some limitations in application. For example, temporal decorrelation and spatial decorrelation can seriously weaken the coherence between the same pixels in a pair of SAR (Synthetic Aperture Radar) images, which makes the processing of interferometry and phase unwrapping be very difficult. Besides, the RCS (Radar Cross Section) of vegetative cover and loose terra changes evidently with time, which would cause the coherence between the same pixels apart of one or several periods to be very bad even not correlate, and InSAR will take no effect on monitoring the surface deformation in these areas. Additionally, atmospheric disturbance can delay the RADAR signal and curve the transmitting path, which will bring errors to phase composition, and any other errors can also influence the quality of phase calculation. All of these can lower the precision and reliability of InSAR results.Due to these factors, it always needs to choose higher coherence image pairs from a mass of SAR data for interferometry processing. In this case, the utilization ratio of SAR data is very low. It must have strict requirements on the parameters of satellite's sensor character, repeat period and spatial baseline of repeat orbit and so on. But it's usually difficult to satisfy these conditions, so it restricts the application fields, and InSAR can not be used more widely.In order to resolve these problems, many researchers (both domestic and foreign) have been developing new technology. In these technology, the PSInSAR (Permanent Scatterer InSAR) proposed in 2001 by A. Ferretti from the company of Tele-Rilevamento Europa and the CRInSAR (Corner Reflector InSAR) proposed in 2002 by Xia Y. from GeoForschungsZentrum Potsdam Germany are more typical. These algorithms conquer the limitations of conventional InSAR and make InSAR can be applied to monitoring of surface deformation in lower-coherence areas, which broadens the application fields of InSAR technology. Although CRInSAR and PSInSAR can improve the utilization ratio of SAR data and the precision of the results effectively, the author finds that CRInSAR and PSInSAR have strong compatibility and can compensate each other very well. If combining them, it will have more advantages. So, this work proposes an algorithm for CR and PS D-InSAR joint calculation, and demonstrates whether this algorithm can effectively improve the precision of InSAR results.Under such a background, and supported by the State Natural Scientific Foundation of China: Research and Preliminary Application of Small Deformation Monitoring Based on CR and PS InSAR (40574007), and the research project (Cooperate with Exploration and Production Research Institute, Sinope): Monitoring Landslides' Deformation in The County of Zichang in Shanxi Province where the pipeline passes by D-InSAR and CRInSAR, some groping research on theory and methods have been made. Based on the previous research, I propose some methods to deal with problems.The thesis consists of six Chapters, including:Chapter one is the introduction, focuses on the basis of CRInSAR and PSInSAR, and proposes the problems to resolve. The beginning of Chapter one analyzes the limitations of conventional InSAR technology, and introduces the concepts of corner reflector and permanent scatterer, compares their RCS with common earth targets. Here the relationship between coherence and the DEM precision of InSAR is also analyzed. Then, it introduces the characteristics and research development of CRInSAR and PSInSAR. By comparing them with conventional InSAR, the advantages of them are clearly presented. It also analyzes their demerits. On the basis of these analyses, it proposes the problems and significance, and puts forward the research contents and method.Chapter two presents the theory of the algorithm for CR and PS D-InSAR joint calculation, this is the core of the thesis. Firstly, it introduces the theory and data processing methods of conventional InSAR particularly. Then, it discusses the algorithm for CR and PS D-InSAR joint calculation, including the technical precondition, theory foundation and data processing flow. In the discussion, it specially introduces the composition and calculation method of interferometric and differential interferometric phase, PS selection principle and standard, also the key technology about phase unwrapping, and compares it with conventional InSAR in the method and accuracy.Chapter three deals with the tasks about corner reflector installation and permanent scatterer selection. Firstly, by investigation in the field and optical remote sensing interpretation, it clarifies the geological structure background and geological calamity situation of the study area, and analyzes the dynamical factors of the movement, thereby the key monitoring area is chosen. Then, based on the previous research accumulation, the corner reflectors are improved, designed, made and installed in the study area. Then, the SAR data are obtained and processed preliminarily. According to the results, permanent scatterers are selected.Chapter four presents the analysis of corner reflectors' image characters and the correction method of parameters in comer reflector installation. This part is very important in the whole research. Firstly, it obtains the character information of corner reflectors in the SAR data. Then, on the basis of analysis the relationship between corner reflectors' image characters and satellite incidence angle, earth's curvature, it suggests the correction method of corner reflectors' orientation angle and elevation angle. And finally it programs the method, which could bring convenience and reference to the persons who will install comer reflectors in the future.Chapter five states the data processing by the algorithm for CR and PS D-InSAR joint calculation. This part is necessary to the algorithm validation. Firstly, it carries out InSAR analysis to all of the data obtained. Then, it processes the 10 scenes of SAR data in three stages according to the time when installing CRs, including the conventional InSAR processing of the 7 scenes of data which were obtained before CRs installation. The joint calculation is made for the 3 scenes of data which were obtained after CRs installation, and the processing of the top-left corner in the image with the joint calculation algorithm using all of the 10 scenes of data. By these processing, it gets the deformation velocity and DEM error of all the PSs whose coherence are above the threshold specified. Thereby, it validates the feasibility of the algorithm about the joint calculation. Then, it assesses the precision of these results, and proves the algorithm's character of high precision. Also, it compares the algorithm with GPS and optical leveling. Finally, it analyzes the prospect of InSAR application in engineering projects.Chapter six is the conclusion. By researching the algorithm for CR and PS D-InSAR joint calculation, the innovations are clearly presented, which include: 1) Proposes the algorithm for CR and PS D-InSAR joint calculation, and carries out validating and preliminary application of it; 2) Proposes the method of permanent scatterer selection based on two principles which are coherence and amplitude, and accomplishes the PS Selection; 3) Proposes the correction method of parameters in corner reflector installation. This chapter also analyzes the problems and shortages in this work, and suggests the treatment method, expects these problems can be solved in the future.