# Analyses of GLONASS and GPS+GLONASS Precise Positioning Performance in Different Latitude Regions
## 5 Conclusions  
It has been more than 10 years since GLONASS restored its full constellation. A solid understanding of the positioning performance of GLONASS and its contribution to the multi-GNSS is important in muti-GNSS positioning applications. This paper presents the performance of GPS, GLONASS, and GPS+GLONASS with both DD network and PPP processing strategies in different latitude regions. According to the statistical analysis results of the current study, the following conclusions can be drawn:  
1. The data integrity rate of GLONASS is lower than that of GPS;
2. Both GPS and GLONASS have the mean maximum number of visible satellites in high latitudes; however, the mean elevation angle of GLONASS is higher than that of GPS;
3. GLONASS has a comparable or even better positioning accuracy than GPS in high latitude regions, and the coordinates of GPS+GLONASS show the best accuracy;
4. GPS stand-alone mode gets the best positioning accuracy in middle latitude regions, and the additional GLONASS observations show no positive impact on GPS+GLONASS processing;
5. GLONASS shows the worst accuracy in low latitude regions, but the adding of GLONASS can improve the positioning accuracy of GPS+GLONASS processing mode when compared to GPS-only processing mode;
6. The addition of GLONASS will reduce the convergence time and improve the accuracy of ZTDs for PPP processing in high, medium, and low latitude regions. Figure 16: The RMSE of ZTDs estimated with PPP. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Region**System** & **G (mm)** & **R (mm)** & **G + R (mm)** & **R/G (\%)** & **G + R/G (\%)** \\ \hline High latitude network & 4.84 & 5.33 & 4.59 & \(-10.10\) & +5.19 \\ \hline Middle latitude network & 6.00 & 6.41 & 5.58 & \(-6.82\) & +6.98 \\ \hline Low latitude network & 8.23 & 9.39 & 7.59 & \(-14.08\) & +7.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: The mean RMSE of ZTDs estimated with the PPP of each network and their comparison between different processing modes (The positive red and negative green values indicate the percentage increment and reduction of accuracy, respectively). Overall, for high-precision positioning users, GLONASS can be used as a stand-alone solution in high latitude regions. The inclusion of GLONASS as a combined multi-GNSS component in high and low latitude areas is advised. The addition of GLONASS observations is always recommended for PPP users of meteorology information. Conceptualization, Y.Z. ; Data curation, Y.Z. ; Investigation, Y.Z. ; Software, F.Z. ; Resources, G.N. ; Validation, Y.Z. and F.Z. ; Formal analysis, Y.Z. and C.Y. ; Visualization, Y.Z. ; Writing--original draft preparation, Y.Z. ; Writing--review and editing, C.Y. and Y.Z. ; Supervision, S.L. ; Funding acquisition, C.Y. All authors have read and agreed to the published version of the manuscript. This project is funded by the National Key Research and Development Program of China (No. 2020 YFB0505802) and the Fundamental Research Funds for the Central Universities (2652017105). The GNSS data used in this paper are provided by CDDIS ([[https://cddis.nasa.gov/](https://cddis.nasa.gov/)]([https://cddis.nasa.gov/](https://cddis.nasa.gov/)), accessed on 10 August 2021). The precise GNSS products are available from CODE ([[http://ftp.aiub.unibe.ch/CODE](http://ftp.aiub.unibe.ch/CODE)]([http://ftp.aiub.unibe.ch/CODE](http://ftp.aiub.unibe.ch/CODE)), accessed on 18 August 2021). The VMF1 troposphere mapping functions were obtained from VMF Data Server ([[http://doi.org/10.17616/R3](http://doi.org/10.17616/R3) RD2H]([http://doi.org/10.17616/R3](http://doi.org/10.17616/R3) RD2H), accessed on 20 August 2021). The ocean tide model was downloaded from the Ocean tide loading provider ([[http://holt.oso.chalmers.se/loading/index.html](http://holt.oso.chalmers.se/loading/index.html)]([http://holt.oso.chalmers.se/loading/index.html](http://holt.oso.chalmers.se/loading/index.html)), accessed on 10 August 2021). The authors thank the IGS for providing GNSS data and products. The authors declare no conflict of interest.