| With the rapid development of industries like intelligent transportation,autonomous driving,the demand for high-precision real-time location services is becoming increasingly urgent.Real-Time Kinematic positioning(RTK),as the most widely used GNSS positioning technology,has high positioning accuracy and fast convergence speed,and is an important technical means to provide high-precision location services.However,for long-distance RTK,there are still problems such as low ambiguity fixation,low success rate,poor interpolation accuracy of atmospheric error,slow convergence speed and poor positioning accuracy of longdistance RTK users.With the completion of China’s Bei Dou-3 Navigation Satellite System(BDS-3)and the improvement of the Galileo system,more and more satellites support quad and above frequencies,leading multi-frequency multi-system GNSS into a new era.Compared with the existing triple-frequency combined observation theory,the quad-frequency/fivefrequency observation values can be able to provide more combinations with excellent performance,as the same time,the multi-system can enrich the number of available satellites and strengthen the spatial geometry,which provides new technical conditions for the improvement of positioning accuracy,reliability and convergence speed.Therefore,taking BDS-3 quad-frequency/five-frequency data processing as the core,this thesis conduct researches on the rapid ambiguity resolution of Network RTK server and the rapid precision positioning of RTK user in multi-frequency and multi-system GNSS,which mainly involves:(1)the rapid ambiguity resolution model of long-distance reference stations,(2)the interpolation model of regional atmospheric error,(3)the fusion RTK model with mutifrequency and multi-system.Based on these algorithms and models,a fast precision positioning system compatible with BDS-3 and other GNSS systems is established,improving the reliability,real-time and continuity of positioning,which also promotes the application of Beidou/GNSS in the field of transportation.The main work and contributions are as follows:(1)The observation quality,compatible interoperability and anti-multipath ability of BDS-3’s new and old frequencies are systematically analyzed.Based on the inter-station single difference model,the observation quality of each frequency and each system is analyzed,and the stochastic models are established by the functions of exponent.Then,the pseudorange and carrier DISB of BDS-3 and BDS-2/GPS/GAL at the same frequency are analyzed,and the compatible interoperability characteristics of GNSS systems are verified.In addition,the double-difference model and wavelet denoising are used to compare the multipath of BDS-3’s different frequencies,and the anti-multipath ability of each frequency is sorted from strong to weak: B3 I,B2a,B1 C and B1 I.(2)A rapid ambiguity resolution method(MFIW)for quad-frequency/five-frequency reference stations is constructed,which solves the problem that the success rate of ambiguity resolution between long-distance reference stations is not high and the calculation of multifrequency data is time-consuming.In addition,the residual tropospheric error is estimated by constructing multiple ionospheric observations,which further improves the success rate of ambiguity resolution.The results show that the fixing rate of over 99.4% can be reached by rounding with MFIW model,and the fixing rate increased to more than 99.7% after correction of residual troposphere.At the same time,the model is used for Galileo quad-frequency observations,and the success rate of ambiguity fixing is also greatly improved compared with the traditional ionosphere-free(IF)model.(3)An adaptive station selection method for atmospheric error interpolation is proposed,which can adaptively select the optimal reference station in real time according to the distance and relative orientation between reference stations and user,which solves the problem that the interpolation accuracy decreases when some reference stations are disconnected.The results show that under the simulation of base station disconnected,the interpolation accuracy of tropospheric wet delay and ionospheric delay are increased by 37.3% and 27.8%,respectively,which can significantly improve the convergence speed and positioning accuracy of RTK users.(4)Three multi-frequency RTK positioning models,i.e.,the dual-IF(DIF)model,the multi-frequency fusion geometry-based(GB)model and the multi-frequency ionospherereduced(IR)model are constructed,which solved the problems of slow convergence speed and poor positioning accuracy caused by atmospheric error.The convergence speed,positioning accuracy and calculation time of DIF,GB and IR model are comparatively analyzed,and the enhancement effect of multi-frequency and multi-system fusion on RTK positioning is discussed.The results show that the positioning accuracy of the GB model is centered,the convergence speed is the fastest,and it is suitable for short baseline and long baseline positioning at the same time,but the operation speed is the slowest due to the large matrix dimension.The positioning accuracy of the IR model is the worst,but the model is the simplest and has the fastest operation speed.The DIF model has the highest positioning accuracy without sacrificing too much computing speed,and the convergence speed is comparable to that of the GB model.In addition,the combination of BDS-2 and BDS-3 can achieve reliable fixing by single epoch under both VRS and long baseline positioning,and can significantly improve the anti-occlusion ability.After the ambiguity is fixed,the positioning RMS of U and NE direction are better than 3cm and 1cm,respectively.(5)A multi-frequency and multi-system RTK fast precision positioning system was established.Based on the above algorithms,the foundation enhancement system software is improved,and the multi-frequency and multi-system RTK positioning models proposed in this thesis are verified in the fields of bridge deformation monitoring and intelligent compaction quality monitoring.For the application of bridge deformation monitoring,the filtering algorithm with additional motion constraints is used to improve the success rate of ambiguity fixing;an improved multipath mitigation model(MHM＿V)is proposed,which effectively improves the reliability and accuracy of GNSS positioning for bridge deformation monitoring.A quality control strategy using road information constraints is proposed for the intelligent compaction scenario,and combined with multi-frequency and multi-system observations,the reliability and accuracy of GNSS for road edge determination and elevation,thickness measurement are improved. |
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