Research On BDS/GPS Dual-system And Multi-frequency Single-epoch Positioning Method

At present,as GPS system is becoming mature,China's BDS system is showing a rapid growing trend,and the global navigation satellite system has entered an era of comprehensive construction and development.BDS is a satellite navigation system which broadcasts triple frequency signal with the whole constellation.Multi-frequency observations linear combination can obtain better observed values,and the noise analysis of pseudorange observation is the premise to improve the positioning accuracy.This paper focuses on BDS/GPS multi-frequency single epoch positioning and has discussed the topics of multi-frequency observations linear combination,noise analysis of pseudorange observation,and BDS/GPS single epoch positioning models.The main research contents and conclusions are as follows:1.The basic theory of GNSS positioning is discussed in detail,and multi-frequency observations linear combinations are analyzed.First,the constellation structure,signal structure,time system and coordinate system of BDS and GPS systems are introduced respectively.Then,the GNSS positioning errors and error eliminating methods are analyzed.The optimal under different baseline lengths are selected based on the characteristics of multi-frequency linear combination observations.2.The characteristics of pseudorange noises of BDS system are analyzed.The pseudorange noises of single frequency,dual frequency,and triple frequency boards are tested respectively.The experiment results show that the satellite altitude angle has a certain effect on pseudorange noise.As for different constellations of BDS,the pseudorange noises of the corresponding frequency points are in the same order of magnitude,but for an individual satellite,the pseudorange noises of three frequency points are different.When the satellite altitude angle changes,the pseudorange noise ratios of three frequency points remain stable.For the SiNan K508 board,the ratios of BDS pseudorange noise are 0.57 and 0.26.The pseudorange noise is stable with time and it will not change when there is no special environmental interference.3.BDS/GPS multi-frequency single-epoch positioning models are researched,mainly including single frequency pseudorange difference model,dual frequency ionosphere free pseudorange difference model,triple frequency ionosphere free noise minimum model,BDS extra wide lane positioning model,BDS/GPS wide lane positioning model,and ionosphere free combination positioning model,triple frequency ionosphere free noise minimum model on noise weigh is proposed.The experiment results show that,for the 18km baseline,B3 has the highest positioning accuracy in BDS single frequency pseudorange difference models.The positioning accuracy of BDS triple frequency ionosphere free pseudorange positioning model is significantly improved after GPS ionosphere free observations are added.The positioning effect can be improved after using pseudorange noise weight.4.The positioning performances of the models under different baseline lengths are tested.For the 8km,26km,41km and 74km baselines,the plane and vertical positioning accuracies of BDS extra wide lane positioning are better than 0.2m,for the 8km baseline,the plane and vertical positioning accuracies of BDS/GPS wide lane positioning are respectively better than 0.05m and 0.1m,the success rate of fixed-ambiguity is 100%;for the 26km,41km,and 74km baselines,the plane and vertical positioning accuracies of BDS/GPS wide lane positioning are better than 0.2m,the success rate of fixed-ambiguity are respectively 96.1%,95.6%and 90.7%.Experiment results show that,for short baselines,BDS extra wide lane positioning model and BDS/GPS wide lane positioning model can be used in single-epoch navigation and positioning.For medium baselines,BDS extra wide lane positioning model can be used in single-epoch navigation and positioning.