BDS/Galileo四频精密单点定位模型性能分析与比较

Analysis and comparisons of the BDS/Galileo quad-frequency PPP models performances

北斗卫星导航系统和Galileo卫星系统都可以提供4个频率信号上的服务。本文通过与双频无电离层模型(DF)比较,评估分析了4种BDS/Galileo四频PPP模型性能,即四频无电离层双组合模型(QF1)、四频无电离层组合模型(QF2)、四频非差非组合模型(QF3)和附加电离层约束四频非差非组合模型(QF4),同时通过等价性原则理论上证明了QF1、QF2、QF3模型的等价性。此外,用1个月参考站的静态数据和1组动态数据分析了四频静态,仿动态和动态PPP性能。试验结果表明,BDS-3 B1C和B2a新频点伪距噪声要略大于B1I和B3I信号,Galileo卫星4个频率上的伪距噪声相差并不明显。对于静态和仿动态PPP模型,QF1、QF2和QF3模型定位性能基本上一致。通过附加外部电离层约束,四频PPP模型性能受到影响,BDS(BDS-2+BDS-3)静态QF4模型相比于QF1、QF2和QF3模型平均收敛时间分别减少了4.4%、4.4%和5.4%,Galileo静态Q4模型平均收敛时间相比于Q3模型增加了16.8 min。对于动态PPP,四频PPP模型相比于双频PPP性能得到提升显著,相比于QF1模型,BDS和Galileo单系统QF4模型三维定位精度分别提高了11.4%和31.4%。BDS/Galileo双系统PPP性能要优于单系统PPP。

Chinese BeiDou navigation satellite system(BDS)and Galileo system can provide the services of quad-frequency observations.In this paper,we assess the BDS/Galileo quad-frequency precise point positioning(PPP)models,i.e.,PPP model with two ionosphere-free combinations(QF1),PPP model with one ionosphere-free combination(QF2),undifferenced uncombined PPP model(QF3)and ionosphere-constrained undifferenced uncombined PPP model(QF4),by comparing the dual-frequency ionosphere-free PPP model(DF).The equivalence of the QF1,QF2 and QF3 models is theoretically demonstrated by the equivalence principle.The static and simulated kinematic PPP performances are evaluated and investigated with one-month period observations from the network stations and the kinematic PPP performances are verified with a kinematic experiment in the campus.The results show that the pseudorange noises of BDS-3 B1C and B2a signals are larger than the B1I and B3I signals and the pseudorange noises differences for the Galileo quad-frequency signals are not obvious.The performances of the QF1,QF2 and QF3 models are basically consistent for the static and simulated kinematic PPP.By adding the external ionospheric constraint,the quad-frequency PPP performances are affected.Compared to the QF1,QF2 and QF3 models,the mean convergence time of the static BDS(BDS-2+BDS-3)model are reduced by 4.4%,4.4%and 5.4%,respectively.The mean convergence time of static Q4 model increases 16.8 minutes when compared to the QF3 model.Compared to the dual-frequency PPP,the quad-frequency kinematic PPP performances are obviously improved.The three-dimensional positioning accuracy of BDS and Galileo QF4 models are improved by 11.4%and 31.4%,respectively,when compared to the QF1 models.Furthermore,the BDS/Galileo kinematic PPP models perform better than the single-system solutions.