**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:


Overall, for high-precision positioning users, GLONASS can be used as a standalone 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.

**Author Contributions:** 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.

**Funding:** This project is funded by the National Key Research and Development Program of China (No. 2020YFB0505802) and the Fundamental Research Funds for the Central Universities (2652017105).

**Data Availability Statement:** The GNSS data used in this paper are provided by CDDIS (https: //cddis.nasa.gov/, accessed on 10 August 2021). The precise GNSS products are available from 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/R3RD2H, 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, accessed on 10 August 2021).

**Acknowledgments:** The authors thank the IGS for providing GNSS data and products.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

