| Since November 2017,the majority of China's third BeiDou Navigation Satellite System satellites have been launched.The construction of the basic system of Beidou-3 was completed by the end of December 2018,and 20 satellites have been put into operation so far.The completion of the basic system of Beidou-3 is a key step for the BDS to reach the world.In order to ensure the accuracy and reliability of its service,t is necessary to analyze the single point positioning performance of the basic system of Beidou-3.Based on the measured data,this paper focuses on the quality of the pseudorange observation of the Beidou-3 satellite,evaluates the ionospheric model of the BDS-3,and discusses the pseudorange single point positioning accuracy of the BDS-3.Its positioning performance was evaluated and analyzed.The works and achievements of this paper mainly include:(1)This paper introduces the new technologies and corresponding evaluation methods adopted by the basic system of Beidou-3.The new frequency navigation signal and users' algorithm broadcasted by the BDS-3 are introduced in detail.Combined with the existing evaluation strategies,the methods and indicators for evaluating the positioning performance of the BDS-3 are determined.(2)In order to evaluate the pseudorange quality of the BDS-3,based on a large amount of real-world data from Beidou-3 satellites in seven consecutive days,this paper analyses the basic performance of the BDS-3 signal including data integrity,satellite visibility,signal to noise ratio characteristics and multipath characteristics.The results show that there is no obvious pseudo-range error related to the satellite elevation angle of the Beidou-3 satellite signal;the multipath error RMSE of the B1 I and B3 I signals of the BDS-3 are about 0.518 m and 0.479 mrespectively,and the multipath error RMSEofthe new signals B1 C and B2 a is about 0.329 m and 0.365 m respectively.Compared with the BDS-2,the multipath error RMSE of the B1 I and B3 I signals of the BDS-3 is improved by 15.4% and 10.6%,respectively;The spatial signal error of the BDS-3 is better than that of the BDS-2,and its root mean square error is about 1 meter.(3)Based on the high-precision ionospheric grid products,the accuracy of the ionospheric model of the BDS-3 was evaluated,and the influence of different ionospheric models on the pseudo-point single-point positioning accuracy was analyzed.The results show that in the global model,compared with the GPSK8 model,the correction accuracy RMSE of the BDGIM model in the high latitude and mid-latitude regions is increased by about 70.3% and 45.7%,respectively.In the regional model,compared with the BD2K8 model,the Klobuchar model of the BDS-3 broadcasting improved the accuracy of RMSE in the high latitude,mid-latitude and low latitude regions of the northern hemisphere by about 3.7828%,4.918%,and 5.1515% respectively;When using pseudorange point positioning method in the BDS-2 or the BDS-2 and BDS-3,It is recommended to use the BD3K8 model;It is recommended to use the BDGIM model when using the B1 I,B3I and B1 C of the BDS-3,and the BDGIM model is recommended when using the GPSK8 model.(4)Based on the measured data,the pseudorange positioning performance of each frequency point of the BDS-3 is analyzed through dynamic and static positioning modes.The focus is on the static positioning accuracy of the pseudo-point single-point positioning performance of each frequency point of the BDS-3 and its non-ionosphere combination is analyzed,and the positioning performance of of the BDS-2,the coalition ofBDS-2 and BDS-3 is compared.The results show that on the Chinese territory the horizontal accuracy of the BDS-3 is better than 4m,and the elevation accuracy is better than 5m.The positioning accuracy of each frequency of the BDS-3 from high to low is: B1C?B2a?B3I?B1I;The horizontal accuracy of the coalition of BDS-2 and BDS-3 is better than 2m,and the elevation accuracy is better than 3.5m;Compared with the BDS-2,the positioning accuracy of the B1 I frequency of thecoalition of the BDS-2 and the BDS-3 is increased by about 29.28% and 14.45% in the horizontal and elevation directions respectively.The positioning accuracy of the B3 I in the horizontal and elevation directions is increased by about 29.44% and 24.53%,respectively;The dual-frequency positioning accuracy of the BDS-3's B1 C and B2 a is significantly better than the accuracy of the B1 I and B3 I,Specifically improved about 113.66% and 133.22% in the horizontal and elevation directions respectively;The horizontal accuracy RMSE value of the single-frequency dynamic pseudorange positioning of the BDS-3 is better than 10 m,and the elevation accuracy RMSE is better than 6m.The horizontal precision RMSE value of the single-frequency dynamic pseudorange positioning of the the coalition of BDS-2 and BDS-3 is better than 4.5m.The RMSE of elevation accuracy is better than 3m. |
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