| In recent years, flourishing development of GNSS including GPS, GLONASS, Galileo and China’s Compass satellite navigation system promotes profound revolution in the field of navigation and positioning, leading to increasingly widespread applications, particularly in geosciences field which has always being an important issue for scholars to be committed to research.Continuously Operating Reference Stations (CORS) is a newly developed product from comprehensive and deep integration of GNSS navigation and positioning technology, computer science and digital communication. And it provides an important infrastructure to carry out GNSS application research. About one hundred CORS have been established in China, and there are some pronounced problems, mainly in lack of attention to applications. Single application mode limits the potential value of CORS. Especially, provincial CORS are based on real-time undifferenced positioning, leading to substantial applications in geodynamics, atmosphere, seismology and oceanography still in their infancy. This dissertation aims at digging out potential application value of CORS, extending its application field and breaking through key issues in geoscience applications.In the past, double-difference positioning approach was always used for the research of geoscience applications of CORS. In recent years, the increasing maturity of the PPP technology offers a new way for CORS geoscience-application research. Compared to the double differenced positioning approach, precise point positioning (PPP) retains more observations with a simple model, unlimited distances, without reference station, even point accuracy and high processing efficiency. As a result, it has been widely applied in many fields. Based on PPP technology, this dissertation systematically studied applications of regional CORS to geoscience field, focus on PPP inversion methodology and spatial-temporal characteristics analysis of zenith atmospheric precipitatable water, PPP coordinate time series analysis and regional velocity field estimation, PPP algorithm for co-seismic displacement from single epoch. Specific contents and main achievements of this dissertation are summarized as follows:1) The status of domestic and international CORS system construction and application is summarized, and the importance of geoscience application using CORS is analyzed. The latest development of PPP-related key technologies is comprehensively reviewed, and PPP-based geoscience applications using CORS in view of significant advantages of PPP are proposed.2) Several key problems of PPP are studied, including the function model, stochastic model and parameter estimation etc. Error sources of PPP are analyzed, and strategies of error elimination or reduction are proposed. The accuracy of the static and dynamic PPP is assessed using TriP software, and their standard deviation of static and dynamic positions are±0.0030m,±0.0031m,±0.0048må'ŒÂ±0.0104m,±0.0136m,±0.0291m, respectively, which lays the theoretical foundation for the following application research of the PPP-based geoscience.3) Zenith perceptible water vapor inversion methods, temporal and spatial variation analysis using PPP are studied. Fundamental theory and methodology of CORS in ground-based GPS atmospheric sounding are studied based on the determination of local troposphere weighted average temperature as well as the analysis of temporal and spatial variation of zenith water vapor, and a multivariate nonlinear model on the basis of regional troposphere weighted average temperature is proposed and it is first used to establish Jiangsu Province troposphere weighted average temperature model. After verification, accuracy of this model achieves±2.91K better than that of Bevis empirical model+3.48K. the applicability analysis of regional tropospheric model are emphatically studied. Besides, with the tracking data for the past five years of JSCORS, the temporal and spatial variation of zenith water vapor is analyzed. Temporal characteristics of PWV including annual, seasonal, monthly and daily variation are deeply analyzed, and relationship between PWVand longitude/latitude variation as well. The resultant PWV variation shows strong relationship to latitude variation, and weak connection to longitude variation.4) Coordinate time series is analyzed and regional velocity filed is determined using PPP. Based on the static PPP, time series of regional CORS are solved. After regional spatial filtering, periodic and noise characteristics of GPS base stations are analyzed. Spectrum analysis of coordinate time series indicates that periodic movement dominates in U direction, most fudicial stations show significant characteristics of annual period in N direction and semi-annual period in E direction. MLE (Maximum Likelihood Estimation) analysis suggests the best noise model for N and E components is the combination of white noise+flicker noise+random walk noise, the the best noise model for U components is combination of white noise+flicker noise. Besides, comparison of regional velocity field considering colored noise and the one from double difference method presents a systematical difference within3mm/yr, which verifies correctness of PPP.5) Coseismic displacement determination method using single epoch PPP is investigated. In this dissertation, the basic theory of coseismic deformation monitoring based on the high frequency GPS data is researched, and especially on the filtering method for positioning results. Accounting for segments’ similarity, an improved sidereal filtering method is proposed based on conventional sidereal filtering method. That is, before building filtering operator, the segments’ similarity of the residual coordinates time series between earthquake occurrence and former day/following day is firstly determined, and filtering is performed based on similarity index according to the weight of each day. The simulation results show that the improved sidereal filtering can effectively improve the single epoch positioning accuracy and reliability, completely overcome the defects of traditional filtering method, and is beneficial to batch processing without manual intervention. Finally, the coseismic displacements of Mw9.0Tohoku-oki earthquake are analyzed with some GPS continuous stations located along China’s east coast using epoch by epoch PPP and improved sidereal filtering technique proposed in this dissertation. The result shows an apparent displacement along horizontal and vertical directions with amplitude about10cm. However, after the earthquake, there is no obvious permanent displacements more than1cm in agreement with related results at home and abroad, which verifies effectiveness of coseismic displacement analysis using PPP.6) Integrated application and value-added service of regional CORS base on the research of three key fields of geoscience applications are discussed. Systematic services can be classified into two groups:basic application service and higher-level application service (value-added service) in terms of CORS service nature. Their corresponding main contents and key technology difficulties are summarized. The field of applications services are expanded from single real-time positioning to other geoscience applications, and they are of important reference value for the developments of value-added services with regional CORS. |
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