Research On Multi-GNSS Precise Orbit Determination Theory And Application

With hot competition of spatial navigation resource, satellite navigation system has been established worldwide, which is of great significance to protect national benefits, economy and military security. After successful establishment of the United States and Russia, the European Union is actively developing their own global satellite navigation system together with our country. To date, coexistence and development of four kinds of global satellite navigation system (that is GPS/GLONASS/COMPASS/Galileo) have initially taken shape, which would form the new generation global satellite navigation system named GNSS. In order to realize compatibility and interoperability of various navigation systems, multimode receivers became the inevitable choice for satellite navigation positioning from GPS to GNSS, so as to promote the development among a new research focus on data fusion of multi-navigation systems.Navigation satellite constellation functions as a dynamical datum for navigation positioning terminal, of which the key is to provide navigation satellite orbit and clock error products with unified temporal and spatial datum so as to solve problems of compatibility and interoperability of various navigation systems, together with Multi-GNSS data fusion. Recently, technology of Multi-GNSS integrated precise orbit determination (POD) has become an important research direction in the GNSS POD, which listed formally as one of the three main development programs by international IGS organization in 2008.To sum up, aiming at the natural trend of the coexistence and compatible interoperability of multi-satellite navigation systems(GPS/GLONASS/COMPASS/Galileo), implementation of research on the integrated POD theory, technology and method based on Multi-GNSS is a necessity, which is not only accordance with international development trend, but also has strong current demand.Taking the aim to solve problems of multi-mode GNSS integrated POD and satellite clock error determination; this dissertation paper discussed its mathematical model, key technology and algorithm realization in detail. Then based on the platform of Position And Navigation Data Analysist (PANDA), Multi-GNSS integrated POD system has been independently developed, realizing precise orbit determination for multi-satellite navigation systems based on original observation data and solving problems of multi-GNSS interoperability from aspect of satellite orbit processing. Finally experiments of integrated orbit determination using real data from GPS/GLONASS/GALILEO and simulated COMPASS orbit determination have been tested in order to verify the effectiveness of the method and the software. Main contents and contributions of this dissertation include:1,Summarizing current status and development trend of GNSS establishment, POD for navigation satellites, as well as multi-mode GNSS data fusion at home and abroad, then demonstrating the necessity to implement precise orbit and error determination of multi-mode navigation satellite systems under unified temporal and spatial datum.2,Systematically investigating the basic theory of POD for navigation satellites, including coordinate systems and time systems, motion equation and its numerical integration, observation equation and error correction model, together with its algorithm flow of POD for navigation satellites.3,Proposing three kinds of integrated POD methods for navigation satellites according to different current status of four navigation systems (GPS/GLONASS/ COMPASS/Galileo):"Two-step" integrated POD, "One-step" integrated POD, as well as MEO-LEO combined POD. Then from practical implementation of multi-mode GNSS integrated POD and clock error determination, key technologies of temporal and spatial reference frame transformation of multi-mode GNSS and its data preprocessing, together with time deviation resolution between multi-mode GNSS systems have been discussed elaborately.4,Developing Multi-GNSS integrated POD software system based on PANDA platform, illustrating its dynamical model, observation model overall framework, as well as data processing flow, software interface and its characteristics.5,Implementing experiments of integrated orbit determination using real data from GPS/GLONASS/GALILEO and simulated COMPASS orbit determination based on self-developed Multi-GNSS integrated POD software:(?) Realizeing precise orbit determination for Galileo experimental satellites (GIOVE-A, GIOVE-B) with "Two-step" and "One-step" integrated POD method respectively. Different strategies have been used to carry out accuracy evaluation including overlap arc tests and SLR verification. Statistics show that, both methods of "Two-step" and "One-step" could achieve radial orbit precision of 10cm for GIOVE satellites. Besides, signal quality of GIOVE-A satellite has been analyzed in detail from aspects of signal-to-noise ratio, multi-path error of pseudo-range, as well as post-fit error of observables.(?) Accomplishing precise orbit determination of GPS and GLONASS satellites under IGS05 frame using "One-step" integrated POD method, which has been compared with European CODE's orbit products. Results show that the average 3-D orbit precision of GPS and GLONASS satellites could reach 2cm and 6cm respectively. (?) Simulating and achieving precise orbit determination for COMPASS navigation satellite system based on MEO-LEO combined POD method using data from 7 tracking stations inside China and GRACE-A satellite data. Results show that combination of ground reference stations and LEOs could improve GNSS orbit determination precision and strengthen GNSS satellite framework, especially when there is limitation in global distribution of reference stations.(?) According to the COMPASS system's three different period:the initial phase, the transition period, the constellation completion period, designed three integrated POD strategies:regional integrated POD method, single-satellite POD method, full ntegrated POD method.6,Realizing static precise point positioning and kinematic positioning of Multi-GNSS with high-precision and high-sampling rate(50Hz) using actual multi-mode observables:(?) Static precise point positioning experiment shows that adding GLONASS data has no significant impact on positioning precision, with the horizontal repeatable accuracy of Multi-GNSS integrated precise point positioning reaching 1～2mm, while 2-3mm for vertical components, which could be applied in high-precision deformation monitoring and analysis.(?) Post kinematic precise point positioning experiment shows that multi-mode observation data could improve positioning precision in different directions to some extent, especially with 20% improvement in East and Up components, and could partially eliminate unmodelled error relating to stations'surroudings.(?) Both static and kinematic precise point positioning of 13 reference stations belonging to the "Crustal Movement Observation Network of China" located in northeast China show that the Mw9 earthquake of Japan happened on Mar.11,2011 caused obvious deformation in some reference stations located in northeast China, which would result in permanent displacement. Either data processing of combined or single type constellation could reflect deformation displacement of various reference stations, propagation direction of the earthquake, as well as its arriving epoch at various reference stations.(?) Precision of Multi-GNSS kinematic positioning with high-rate (50Hz) has been tested based on high-accuracy verification platform allocated with multi-mode GNSS receivers. Experimental results show that technology of GNSS integrated data processing could obtain correct trajectory of satellites, from which would reflect its true operating status more accurately.