The Study Of GNSS Real-time Positioning Algorithm Using Large-scale CORS Network

Local area augmentation system based on large-scale CORS network which mainly takes long rang network RTK algorithm, not only can reduce the construction cost of base stations, but also can resolve the problem of network RTK system construction in the region where we have difficulties in the base stations construction. The positioning theories of long range network RTK and methods of processing all kinds of errors are introduced and researched fully in this dissertation. The resolution of ambiguities between long range base stations (generally 100-200km) are firstly researched and completed. Then the high-precision model of regional errors is established, the error corrections of observations are calculated and the errors on rovers are removed. Meanwhile the methods of dynamic ambiguities resolution on rovers are researched. Finally, the program of the algorithms in this thesis is implemented, and the algorithm is evaluated by test data. The main contents and results of this dissertation are composed by the following parts:(1) The foundational positioning theories of GNSS real-time positioning algorithm using large-scale CORS network, including GNSS carrier phase and pseudo range observations and observation equations, the linearization of GNSS observation equations are discussed. The characteristics of GNSS positioning errors and the processing methods of these errors are introduced. The processing methods of the errors in network RTK positioning, especially the errors which are relative to the long distance such as GNSS satellite orbit error, ionosphere delay error and neutral atmosphere delay error which is mainly troposphere delay, are analyzed in detail.(2) The theories and algorithms of integer ambiguities resolution for GNSS real-time positioning algorithm using large-scale CORS network are deeply researched. On the base of this work, the algorithm of integer ambiguities instantaneous resolution for long-range reference stations is proposed. The methods of errors processing and error corrections theories of observations in the large area which is covered by long range base stations are mainly studied. On the basis of integer ambiguities fixed for long range reference stations, the methods of calculating error corrections in large area by the combined errors are introduced in detail. The methods of frequently-used integer ambiguities resolution are researched. Then the integer ambiguity resolution method for rovers is proposed.(3) The algorithms in this dissertation are programmed and the software has been developed by C++ language. Then the algorithms test and the results analysis are implemented by observation data of CORS net. And the positioning results are at centimeter level. It is proved that the algorithms have good usability in this dissertation.