# Assessment of IRNSS-Only Data Processing: Availability, Single-Frequency SPP and Short-Baseline RTK
## 5 Results and Analysis
### Positioning Accuracy of SPP and Characteristics of ISB Estimates  
In this section, the positioning performance of the IRNSS-only SPP is assessed based on the 14 MGEX stations (see Figure 2). For comparative analysis, the results of the other two cases (GPS-only and GPS/IRNSS) are also provided. The epoch-wise root mean square (RMS) statistics of positioning errors at the same epochs for all the 24-h datasets from the employed seven days and 14 stations are calculated. Figure 9 displays the epoch-wise RMS statistics of positioning errors in the east, north and up directions under two single-system cases, namely IRNSS-only and GPS-only SPP. The epoch-wise positioning accuracy of IRNSS-only SPP is better than 10.0, 11.3 and 13.6 m in the three directions, respectively, but with large fluctuations. The overall positioning accuracy (i.e., RMS statistics of positioning errors over all the available epochs from all the used days and stations) of IRNSS-only SPP is 6.031, 6.015 and 9.668 m in the three directions, respectively. In contrast, the epoch-wise positioning accuracy of GPS-only SPP is better than 0.8, 1.3 and 3.2 m in the three directions, respectively, and the overall positioning accuracy is 0.519, 0.815 and 2.293 m in the three directions, respectively. The analysis shows that under the current constellation conditions, the positioning accuracy of IRNSS-only SPP is far worse than that of GPS-only SPP, even in the service areas of IRNSS. The epoch-wise RMS statistics of positioning errors in the 3D direction for the three cases, namely IRNSS-only, GPS-only, and GPS/IRNSS SPP, are shown in Figure 10. The epoch-wise 3D positioning accuracy is better than 18.3, 3.3, and 3.0 m for the three cases, respectively. The overall 3D positioning accuracy under IRNSS-only, GPS-only, and GPS/IRNSS cases is 12.885, 2.489, and 2.237 m, respectively. Compared with the IRNSS-only SPP, the 3D positioning accuracy of the GPS/IRNSS integrated solutions is improved by 82.6%. In comparison with the GPS-only SPP, the 3D positioning accuracy of the GPS/IRNSS integrated solutions is improved by 10.1%. For further analysis, Figure 11 provides the station-dependent RMS statistics of 3D positioning errors for IRNSS-only SPP. It is indicated that the positioning accuracy is consistent with PDOP performance (see Figure 7). Figure 9: Epoch-wise RMS statistics of positioning errors in the east, north and up directions for IRNSS-only and GPS-only SPP based on the datasets collected at 14 MGEX stations on 7–13 July 2019. The code observation residuals that contain measurement noises and other unmodeled errors can be used as an important index to evaluate the SPP mathematical model. The code observation residuals derived from the GPS/IRNSS SPP based on the datasets collected at 14 MGEX stations spanning seven consecutive days from 7-13 July 2019, are used for analysis. Figure 12 displays the distribution of code residuals for the GPS and IRNSS satellites, as well as the corresponding residual statistics (including the RMS value and average value). The code residuals of GPS are more concentrated than those of IRNSS. The code residuals of GPS are basically within \(\pm\)3 m, and the corresponding varying range of IRNSS is relatively larger (within \(\pm\)4.5 m). The RMS value of the code residuals of GPS is 0.808 m, and is increased to 1.203 m for IRNSS. Regarding the average value of code observation residuals, it is \(-\)0.012 m for GPS, and is increased to 0.050 m for IRNSS. Under the GPS/IRNSS case, the code residuals of GPS and IRNSS satellites approximately obey the normal distribution. Based on the analysis and evaluation, it is indicated that the  
Figure 11: Station-dependent RMS statistics of 3D positioning errors for IRNSS-only SPP at 14 MGEX stations on 7–13 July 2019 (unit: m).