# Performance Analysis of the Korean Positioning System Using Observation Simulation
## 4 Performance Analysis for KPS
### Precise Point Positioning (PPP)  
To show the feasibility of precise positioning on a regional scale for KPS, we examine the performance of different kinematic PPP (KPPP) processing. Figure 10 shows the KPPP positioning accuracy for KPS, GPS, and combined KPS+GPS in the E, N, and U components, respectively. KPS is not available anywhere globally. As clearly shown in Figure 10, the KPS service area is limited only to the East Asia and Oceania regions. KPS KPPP results are very similar to KPS SPP in terms of the  
Figure 8: SPP positioning accuracy. (**a**–**c**) for KPS-only; (**d**–**f**) for GPS-only; (**g**–**i**) for combined KPS+GPS. E, N, and U characters indicate the east, north, and up direction components. In each sub-figure, the ground-track of KPS IGSO orbit is the analemma. The red crosses denote the ground-track of three KPS GEO satellites. characteristics of the positioning errors. As with KPS SPP, the positioning accuracy is relatively high in areas where five or more visible satellite signals on the ground can be tracked. The positioning accuracy of KPS tends to drop sharply with the average number of visible satellites on a regional scale. The positioning accuracy of KPPP is very different from that of SPP. While SPP has meter-level positioning accuracy, KPPP can achieve centimeter-level solutions. As shown in the middle Figure 10d-f, GPS solutions provide stable positioning performance in the regional area. Compared to KPS and GPS, combined KPS+GPS can improve the positioning accuracy significantly. In the KPS service area, it can be seen that the combined KPS+GPS solutions can achieve position accuracy of less than about 1 and 2 cm in the horizontal and vertical components, respectively. Figure 9: This is related to the grids in Figure 8. Position RMS errors at the grid points are expressed as the probability distributions. (**a–c**) for KPS-only; (**d–f**) for GPS-only; (**g–i**) for combined KPS+GPS SPP, respectively. Histograms are calculated by a 95% confidence level with the normal approximation. Note that the left subfigures (**a–c**) have different horizontal scales. For the numerical analysis of KPPP results, we present the probability distribution for the corresponding position RMS errors. Figure 11 is related to the grids in Figure 10. The RMS errors at the grid points are expressed as the probability distributions for KPS, GPS, and KPS+GPS KPP. The averaged values of position errors for KPS are approximately 7.5, 5.8, and 9.1 cm in the E, N, and U components, respectively. The averaged position errors in all three coordinate components were lower than 10 cm. In the fringe of the KPS service area, however, KPS errors can reach to about 40 cm. This indicates that the number of visible satellites can result in large positioning errors in KPPP mode. As shown in the middle Figure 11d-f, GPS is more accurate than KPS. The absolute accuracy of GPS in all components is within a range of 0 to 4 cm. The position errors on average are about 1.0, 1.0, and 2.1 cm in each component, respectively. Moreover, the vertical component for GPS is statistically concentrated on the positioning errors between 1.8 to 3.0 cm. The vertical error is related to the satellite geometry. It is relatively larger than the horizontal one. The positioning accuracy of the combined KPS+GPS was significantly improved compared to KPS and GPS. The averaged position errors were about 0.7, 0.8, and 1.5 cm in each component, respectively. In the KPPP mode, the integration of KPS and GPS can provide higher accuracy, which can be better than 1 and 2 cm for the horizontal and vertical components, respectively. For the bulk of the positioning errors less than 1 cm, the E and N components provide similar performance. Furthermore, the U component presents a large population of positioning errors between 1.2 and 2.0 cm. The positioning accuracy for the combined KPS+GPS was improved compared to GPS by approximately 28.7%, 27.1%, and 30.5% in each component.