Afifi Akram, El-Rabbany Ahmed
Department of Civil Engineering, Ryerson University, Toronto, ON M5B 2K3, Canada.
Sensors (Basel). 2015 Jun 19;15(6):14701-26. doi: 10.3390/s150614701.
This paper examines the performance of several precise point positioning (PPP) models, which combine dual-frequency GPS/Galileo observations in the un-differenced and between-satellite single-difference (BSSD) modes. These include the traditional un-differenced model, the decoupled clock model, the semi-decoupled clock model, and the between-satellite single-difference model. We take advantage of the IGS-MGEX network products to correct for the satellite differential code biases and the orbital and satellite clock errors. Natural Resources Canada's GPSPace PPP software is modified to handle the various GPS/Galileo PPP models. A total of six data sets of GPS and Galileo observations at six IGS stations are processed to examine the performance of the various PPP models. It is shown that the traditional un-differenced GPS/Galileo PPP model, the GPS decoupled clock model, and the semi-decoupled clock GPS/Galileo PPP model improve the convergence time by about 25% in comparison with the un-differenced GPS-only model. In addition, the semi-decoupled GPS/Galileo PPP model improves the solution precision by about 25% compared to the traditional un-differenced GPS/Galileo PPP model. Moreover, the BSSD GPS/Galileo PPP model improves the solution convergence time by about 50%, in comparison with the un-differenced GPS PPP model, regardless of the type of BSSD combination used. As well, the BSSD model improves the precision of the estimated parameters by about 50% and 25% when the loose and the tight combinations are used, respectively, in comparison with the un-differenced GPS-only model. Comparable results are obtained through the tight combination when either a GPS or a Galileo satellite is selected as a reference.
本文研究了几种精密单点定位（PPP）模型的性能，这些模型在非差和星间单差（BSSD）模式下结合了双频GPS/伽利略观测值。其中包括传统的非差模型、解耦时钟模型、半解耦时钟模型和星间单差模型。我们利用国际GNSS服务多GNSS实验（IGS-MGEX）网络产品来校正卫星差分码偏差以及轨道和卫星时钟误差。对加拿大自然资源部的GPSPace PPP软件进行了修改，以处理各种GPS/伽利略PPP模型。总共处理了六个IGS站的六组GPS和伽利略观测数据集，以检验各种PPP模型的性能。结果表明，与仅使用GPS的非差模型相比，传统的非差GPS/伽利略PPP模型、GPS解耦时钟模型和半解耦时钟GPS/伽利略PPP模型将收敛时间缩短了约25%。此外，与传统的非差GPS/伽利略PPP模型相比，半解耦GPS/伽利略PPP模型将解算精度提高了约25%。此外，无论使用何种类型的BSSD组合，BSSD GPS/伽利略PPP模型与非差GPS PPP模型相比，将解算收敛时间缩短了约50%。同样，与仅使用GPS的非差模型相比，当使用松组合和紧组合时，BSSD模型分别将估计参数的精度提高了约50%和25%。当选择GPS或伽利略卫星作为参考时，通过紧组合可获得可比结果。
