BDS-2/BDS-3融合三频精密单点定位模型及偏差特性分析

BDS-2/BDS-3 Joint Triple-Frequency Precise Point Positioning Models and Bias Characteristic Analysis

北斗三号全球卫星导航系统(global BeiDou-3 navigation satellite system,BDS-3)正联合北斗二号(区域)卫星导航系统(BeiDou-2 navigation satellite system,BDS-2)在3个或3个以上频率信号上为用户提供高精度的定位、导航和授时服务。为深度融合BDS-2和BDS-3三频数据,建立了BDS-2/BDS-3三频无电离层组合和三频非组合精密单点定位(precise point positioning,PPP)模型,推导了接收机频间偏差(inter-frequency bias,IFB)和BDS-2与BDS-3时间延迟偏差(time delay bias,TDB)的数学表达式。对PPP定位性能及模型偏差特性进行分析,结果表明:BDS-3能显著增强PPP定位性能,BDS-2/BDS-3融合静态PPP在东、北、天3个方向上的收敛时间和定位精度分别为15.8、7.3、22.3 min和1.2、1.0、1.8 cm,动态PPP收敛时间和定位精度分别为27.3、10.3、33.8 min和2.2、1.7、4.4 cm;三频无电离层组合与非组合PPP的收敛性能和定位精度基本相当,且三频观测值对定位性能提升不明显;IFB和TDB均具有较好的天内稳定性,BDS-2和BDS-3信号IFB天内标准差(standard deviation,STD)可分别达到7.9 cm和3.6 cm,而TDB天内STD可达到8.8 cm。

Objectives:The global BeiDou-3 navigation satellite system(BDS-3)along with regional BeiDou navigation satellite system(BDS-2)is providing users with high-precision positioning,navigation and timing services on three or more frequency signals.To deeply integrate the triple-frequency observations of BDS-2 and BDS-3,we establish the BDS-2/BDS-3 joint triple-frequency precise point positioning(PPP)models and analyze the characteristics of biases arisen in these models.Methods:Using the linear combinations of raw observations,the triple-frequency ionosphere-free and uncombined PPP models are developed.In particular,the mathematical expressions of receiver inter-frequency bias(IFB)and time delay bias(TDB)between BDS-2 and BDS-3 are derived.Results:The experimental results show that BDS-3 can significantly enhance the PPP performance.In static mode,the BDS-2/BDS-3 joint PPP is able to achieve the positioning accuracy of 1.2/1.0/1.8 cm after the convergence time of 15.8/7.3/22.3 min in the east/north/up components.As for kinematic PPP,the convergence time and converged positioning accuracy are 27.3/10.3/33.8 min and 2.2/1.7/4.4 cm,respectively.Conclusions:The convergence performance and positioning accuracy of triple-frequency ionosphere-free and uncombined PPP models are comparable,and the third frequency signal makes a marginal contribution to positioning performance.Both IFB and TDB show the good intra-day stability.The intra-day standard deviations(STD)of IFB can reach 7.9 and 3.6 cm for BDS-2 and BDS-3 signals,respectively,and the intra-day STD of TDB can reach 8.8 cm.