The Analysis And Research Of Error Model In BDS System Dual Frequency Positioning

Compass satellite navigation system is developed by our own satellite navigation system,widely used in China's civilian and military fields,the accuracy of single point positioning is the user has been concerned about.With the Beidou three-band signal broadcast,based on dual-frequency,multi-frequency ionosphere-free combination positioning is our first choice of single point positioning.However,there is such a phenomenon in the Beidou single point positioning: Beidou dual-frequency ionosphere-free combination of positioning accuracy is worse than single-frequency single point positioning.This paper focuses on this phenomenon,analyze the Beidou multi-frequency positioning error sources,and the error modeling,and ultimately to solve the problem of this phenomenon.The main work and innovation of this paper are summarized as follows.Based on the study of Beidou single frequency and dual frequency positioning principle,the characteristics and influence of various error sources are analyzed.The main reasons that lead to Beidou dual frequency positioning accuracy worse are multipath error.It certified that dual frequency positioning error caused by multi-path error may reach 2-3m,and the GEO multipath errors and the assumptions of the constant part are analyzed,the satellite hardware delay error may reach nearly 10 m.The error characteristics of Beidou dual-frequency positioning are analyzed by using a large number of IGS stations for a long time and compared with GPS dual-frequency positioning.The results show that the dual frequency positioning of Beidou system is 60% worse than GPS dual-frequency positioning.The effect of multipath error on dual frequency localization is analyzed.The constant part of GEO multipath is calculated based on the pseudorange and carrier phase.The results show that removal the multipath error can improve the positioning accuracy by 10%.The accuracy of positioning accuracy is almost equal to that of GPS,which indicates that multipath error is an important error source of Beidou dual frequency positioning.This paper analyzes the existing noise multipath correction model for real-time BeiDou dual-frequency positioning.The experimental results show that this model is sensitive to carrier cycle slip.In this paper,the detection and repair of cycle slip are used to correct the noise multipath correction algorithm,which improve the accuracy of multipath correction by 30%,but the data quality requirement is still high.The multi-path real-time correction model based on carrier to noise ratio(SNR)is proposed in order to deal with the multipath error in real time when the data quality is poor,with this error model,dual-frequency positioning accuracy improve about 50%.