Multi-frequency GNSS Precise Positioning Theory And Method Research

With the modernization of U.S. GPS, the establishment of European GALILEO system, the recovery of the Russian GLONASS system, and the implementation China COMPASSⅡ, four satellite navigation systems will provide 120 navigation satellites. multi-frequency multi-system combinations postioning not only can improve the navigation accuracy and reliability, but also can improve the success rate of fixing carrier phase integer ambiguity and reduce the initial time for ambiguity fixed. However, it is not easy to process so many observation data and resovel ambiguity in high dimension, which propose new problem in high-precision multi-frequency GNSS combined navigation and positioning.The multi-frequency high-precision GNSS positioning theory and methods are reseached in this paper, which mainly contains the following sections:1. Simulation of GNSS multi-frequency observationsThe errors of GPS observation are analysis and simulated with the error model, and GNSS satellite constellation are simulated based on the orbit parameters, then the GNSS observation are simulated based on the theory of GNSS positioning, the GNSS simulation software can output multi-system multi-frequency pseudo-range and carrier phase observations.2. New method for carrier phase mixed pseudo-range combination—the least square methodThe original method to resolve the coefficients of carrier phase mixed pseudo-range combination is very complicated and can only resolve 3 frequency combinations, so new method which based on least square method is proposed to resolve the coefficients, it is very easy to understand and can resolve 4 or more frequency combinations.3. New method to detect cycle slip of three-frequency data—Three frequency TurboEdit method Analysis the limitations of cycle slip detection and repair for dual frequency carrier phase data, then the Three frequency TurboEdit method to detect and repair the three-frequency carrier phase cycle slip is introduced, the real observation of the GPS three frequency data (15s interval) is processed, which can effectively detect and repair half-cycle slips.4. GNSS ambiguity resolution methods is studied1) A new search method for ambiguity search—K-Bootstrap MethodSpherical ambiguity search method is analyzed, and for high-dimensional case, the spherical ambiguity search method takes a long time, the paper proposes a new method for ambiguity resolution-K-Bootstrap method, in high dimension case, the new method can greatly reducing search time for ambiguity fixed.2) Introduction of lattice theorythe Lattice theory was introduced to aid the carrier phase integer ambiguity resolution, multi-dimensional Gaussian integers decorrelation is under the LLL reduce law, and further analysis of the performance of LLL reduce, Gaussian integers decorrelation,inverse Cholesky integer decorrelation, and unified integer decorrelation for ambiguity resolution, the results show that:LLL reduce is not only less time consuming, and the Bootstrap can get a higher success rate; uniform integer decorrelation method get the most time consuming, but receive the highest success rate of Bootstrap; inverse Cholesky decorrelation is time-consuming, and with lower success rate of Bootstrap. In high-dimensional case, when the Bootstrap success rate is low, it is more time-consuming to search ambiguity, when the Bootstrap success rate is high, less time-consuming to search ambiguity.3) A new method of sequential ambiguity resolutionA sequential method of ambiguity resolution is proposed, which first transform the ambiguity to new ambiguity combination in the ambiguity region, and then fix them in sequential model, it can reduce ambiguity resolution time while increasing the value of Ratio.4) using Monte Carlo method to validate success rate of ambiguityIntroduce the success rate for ambiguity resolution, including rounding, Bootstrap, integer least squares method. the Monte Carlo method is used to verify the theoretical, the results show that, Bootstrap ambiguity success rate is lower but close to the integer least squares method.5) using Monte Carlo method to validate Ratio valueThis paper analyzes the principle of Ratio test, and using Monte Carlo methods to obtain the distribution of Ratio value in different dimensions, in high-dimensional case, using the experience value of 2 in Ratio would be too conservative, and on this basis, the ambiguity resolve with fixed-failure rate method is introduced.5. Analyzed the performance of multi-frequency GNSS relative positioning1) Analyzed the success rate of single epoch ambiguity resolutionThe success rate of single-epoch ambiguity fixed is analyzed, the success rate of ambiguity fixed in the European region is similar, but in the Chinese region and the surrounding areas, the success rate of ambiguity resolution for COMPASS is much better than the other three systems; relative to a single system, multiple systems can improve the success rate of single-epoch ambiguity resolution.2) Analyzed the multi-epoch ambiguity reolution for long baselineThe KALMAN filter is used to process three-frequency data simulated, the initialization time for ambiguity fixed is studied, the results showed that:compared with dual-frequency, the three-frequency can largely reduce the initialization time for ambiguity fixed, it's RATIO values is lager than dual-frequency, which make it easy to fixed ambiguity when ambiguity is right.