GNSS非组合PPP部分模糊度固定方法与结果分析

Partial Ambiguity Resolution Method and Results Analysis for GNSS Uncombined PPP

在精密单点定位(precise point positioning,PPP)技术中,模糊度固定错误将导致严重的定位偏差,为保证PPP模糊度实现更可靠的固定,需对模糊度子集的选取方式进行优化。提出了一种将质量控制与施密特正交化相结合的PPP部分模糊度固定方法。在全球导航卫星系统(global navigation satellite system,GNSS)多系统融合条件下,选取多模GNSS实验数据,在非差非组合PPP模型中对比分析施密特正交化方法与高度角选星方法,并进行模糊度固定及定位性能验证。结果表明,施密特正交化方法相比高度角选星方法,各天与各站平均历元固定率在静态模式下分别提高了7.74%与11.46%,在仿动态模式下分别提高了7.90%与7.78%;各天与各站的首次固定时间在静态模式下分别提高了22.30%与25.42%,在仿动态模式下分别提高了20.44%与19.65%。在PPP模糊度固定和定位精度方面,多系统融合相比单BDS(BeiDou navigation satellite system)提升效果明显,在95%分位数条件下,水平和高程方向收敛时间分别平均减少20.00 min和19.00 min,水平和高程方向定位精度分别平均改善了1.50 cm和1.12 cm。在非差非组合PPP模型中,采用施密特正交化PPP部分模糊度固定方法可以显著提升模糊度固定性能,改善定位精度。

Objectives:In precise point positioning(PPP)technology,the correct fixing of ambiguity is always an essential part of achieving high-precision positioning.However,the wrong fixing of ambiguity will lead to serious positioning errors.Therefore,it is necessary to optimize the selection of the ambiguity subset to ensure a more reliable fixing of PPP ambiguity.Methods:This paper proposes a PPP partial ambiguity resolution(PAR)method that combines quality control and Gram-Schmidt orthogonalization.By utilizing the multi-GNSS(global navigation satellite system)experiment(MGEX)observations in the un-differenced and un-combined PPP model,the PAR method based on Gram-Schmidt orthogonalization was compared and analyzed with the selected reference satellite method with maximum elevation,and the performance of ambiguity resolution and positioning was assessed under the multi-GNSS conditions.Results:Experimental results show that the average epoch fixing rate of each day and each station based on the GramSchmidt method is improved by 7.74%and 11.46%in the static mode,and 7.90%and 7.78%in the pseudo-kinematic mode,respectively,compared with that of the selected reference satellite method considering the maximum elevation.Meanwhile,time-to-first-fix(TTFF)of each day and each station based on the Gram-Schmidt orthogonalization can be significantly reduced by 22.30%and 25.42%in the static mode,corresponding to an improvement of 20.44%and 19.65%in the pseudo-kinematic mode,respectively,compared with that of the selected reference satellite method considering the maximum elevation.As far as multi-GNSS PPP AR is concerned,multi-GNSS PPP AR has a significant improvement on the convergence time of BDS(BeiDou navigation satellite system)only.The convergence time of horizontal components is shortened by 20.00 min on average at 95%confidence level,and the vertical components are shortened by 19.00 min on average.For the positioning accuracy aspects,the positioning accuracy of horizontal components is improved by 1.50 cm on average,while that of vertical components is improved by 1.12 cm on average.Conclusions:The PPP PAR algorithm based on the Gram-Schmidt method can significantly improve the performance of ambiguity resolution and positioning accuracy.