# Performance Analysis of the Korean Positioning System Using Observation Simulation
## 5 Summary and Conclusions  
In this study, we presented the initial KPS constellation. We also performed simulations to investigate the performance of the designed KPS in the service area. For KPS GEO satellites, the achievable orbit precision with the simulated ground data was approximately 50 cm 3-d RMS compared to the true orbit that we simulated, while KPS IGSO POD was approximately 10 cm. Moreover, the performance indicators for KPS/GPS were analyzed in terms of satellite visibility, SISRE, SPP, and KPPP.  
The area where seven KPS satellite signals are tracked on the ground at the same time is located at 35\({}^{\circ}\) S-35\({}^{\circ}\) N latitude and 90\({}^{\circ}\) E-162\({}^{\circ}\) E longitude.  
With the simulated precise KPS/GPS orbit products, we calculated the orbit-only SISRE for KPS/GPS. The averaged RMS values of the orbit-only SISRE were approximately 4.3 cm for KPS GEO and approximately 3.9 cm for KPS IGSO. The SISRE of KPS IGSO was slightly smaller than that of KPS  
Figure 11: This is related to the grids in Figure 10. Position RMS errors of KPPP at the grid points are expressed as the probability distributions. (**a–c**) for KPS-only; (**d–f**) for GPS-only; (**g–i**) for KPS+GPS. Histograms are calculated by a 95% confidence level with the normal approximation. Note that the left subfigures (**a–c**) have different horizontal scales.  
GEO. However, the SISRE of KPS was relatively large compared to that of GPS. It is directly related to the KPS orbit accuracy.  
The performance of KPS SPP tends to decrease sharply as the distance from the central longitude of IGSO satellites increases. It is directly related to the average number of visible satellites on the ground stations. In addition, the KPS SPP can result in large positioning errors of tens of meters when the number of visible satellites is less than five. The positioning errors for KPS SPP in the service area were about 4.7, 3.9, and 7.1 m for the E, N, and U components, respectively. For the GPS SPP solution, they were about 1.2, 1.4, and 3.1 m for each component. Therefore, it can be seen that the KPS-only SPP derived from the simulation has a poor performance in positioning accuracy compared to the GPS-only SPP. Furthermore, we showed that the combination of KPS and GPS can significantly improve the positioning performance.  
The averaged position errors for the KPS-only KPPP in the service area were less than 10 cm. This indicates that the KPS system can have the capability of precise positioning. In some regions, the errors of the KPS-only KPPP reached about 40 cm. Unlike KPS, the GPS-only KPPP solutions showed high positioning accuracy in the KPS service area. In addition, the positioning accuracy in the KPPP mode was further improved by combining KPS and GPS. With the comprehensive performance of KPS from the simulation, KPS can provide better performance with GPS in the Asia-Oceania region.  
As a result, we presented some predicted performances, including different positioning results in future KPS operating modes. The KPS system is expected to be valuable and contribute to GNSS users.  
Methodology, B.-K.C. and H.G.; software, H.G., B.-K.C., K.-M.R. and M.G.; validation, B-K.C., H.G. and K.-M.R.; investigation, B.-K.C.; writing--original draft preparation, B.-K.C.; writing--review and editing, B.-K.C., K.-M.R., H.G., M.G., J.-M.J. and M.B.H.; visualization, B.-K.C. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors would like to thank GFZ for giving us the opportunity to collaborate with Department of Geodesy. The authors would also like to thank the editor and five anonymous reviewers for their constructive comments. This study was supported by the 2020 Primary Project of the Korea Astronomy and Space Science Institute.  
The authors declare no conflict of interest.