Research On BDS Triple-frequency Precise Point Positioning Technology In Complex Environment

The Beidou Navigation Satellite System is an independent and controllable global navigation satellite position system developed by China,and its strategic importance is selfevident.With the completion of BDS-3 system,BDS navigation satellite system will go deeper into all fields and industries of society.With the development of global navigation and positioning system,complex scenes are inevitable.In order for Beidou system to occupy a favorable position in the future navigation and positioning market,it is necessary to study its positioning performance in complex environment.According to Beidou's advantages of backwardness(the first constellation to broadcast three-frequency signals)and combined with the advantages of precise point positioning,on the basis of in-depth research on the theory and algorithm of precise point positioning,the three-frequency precise point positioning technology of BDS in complex environment is studied in this thesis.Its main work is as follows:(1)The main error sources in the three-frequency precision single point positioning of BDS system were deeply analyzed.the existing precision single point positioning supporting products were sorted out and analyzed,and the precision track differences of IGS analysis centers were compared.Two kinds of three frequency precise point positioning function models are presented and their positioning performance is analyzed experimentally.It lays a foundation for data quality analysis and data location solution.(2)According to the actual possible measurement environment scenarios,three different complex environment scenarios are presented after the summary,including zenical occlusion environment(forest occlusion,etc.),surrounding occlusion environment(urban high-rise occlusion,etc.)and one-way occlusion environment(mountain occlusion,etc.).After that,field data were collected for the above three complex environments.Then,the collected data were analyzed for data quality,including data integrity,multipath effect,signal-to-noise ratio and cycle silp,and the characteristics of observed data in various complex environments were summarized.The results show that the signal quality of BDS is better than that of GPS and GAL.Finally,the accuracy analysis of BDS ultra-fast precise ephemeris and clock difference in the forecast part is carried out,which provides a basis for the real-time dynamic PPP comparison of three-frequency and dual-frequency.(3)In order to control the quality of observations in complex environments and to improve the convergence speed of PPP in complex environments,in the parameter estimation stage,different stochastic model schemes and different ionospheric constraint correction schemes are set,and different schemes are set for each scheme.Solve parameters.The performance of BDS tri-frequency precise single-point positioning under the application of different stochastic models and different ionospheric correction methods is analyzed.The results show that:(1)For the BDS tri-frequency precise single-point positioning solution in various complex environments under different stochastic models,static In positioning,the SNR scheme has the best positioning performance under the TREE station environment,the UNIT scheme has the best positioning performance under the BULD station environment,and the UNIT scheme has the best positioning performance under the MOUN station environment.The ELE scheme has the best positioning performance under the station environment,the UNIT scheme has the best positioning performance under the BULD station environment,and the SNR scheme has the best positioning performance under the MOUN station environment.(2)For the BDS trifrequency precision single-point positioning solution in various complex environments under different ionospheric constraints,in static positioning,the GIM scheme has the best positioning performance in the TREE station environment,and the positioning performance in the BULD station environment.The optimal one is the NO scheme,and the NO scheme has the best positioning performance in the MOUN station environment;in the dynamic positioning,the NO scheme has the best positioning performance in the TREE station environment,and the best positioning performance in the BULD station environment.The best one is the NO scheme,and the best one is the GIM scheme in the MOUN station environment.(4)Aiming at BDS three-frequency real-time dynamic precise point positioning,the satellites with poor ephemeris accuracy were removed based on the analysis of the forecast ultrafast precise ephemeris.The location of each complex environment is solved and compared with the results of dual-frequency location.The results show that there is little difference in convergence rate between the two schemes in the tree-shaded environment,but the convergence rate of three-frequency positioning in the MOUN environment is better than that of twofrequency positioning in the tree-shaded environment.