## 5 GNSS Positioning Performance of Xiaomi Mi 8
### Static Test Analysis
Looking into the results using the time differenced filter, we find that continuous and smooth positioning solutions are obtained for various observation combinations as shown in Figures 14 and 15. When only L1/E1 observations are used, the horizontal error RMS is 1.5-2.0 m and the vertical error RMS is about 2.5 m. The use of dual-frequency GNSS observations reduces the horizontal error RMS to about 1.0 m, and the vertical error RMS to about 1.5 m. For the dual-frequency positioning results with Galileo and GPS measurements, it can be seen that when positioning with all Galileo and GPS satellites, the time differenced filter algorithm positioning error RMS in East (E), North (N) and Up (U) directions is 0.67 m, 0.87 m, and 1.48 m, respectively. The SPP positioning error RMS in E, N, and U is 2.18 m, 2.95 m, and 6.53 m, respectively. The SPP availability is 99.3%. However, when conducting with \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**TD Filter**} & \multicolumn{6}{c}{**SPP**} \\ \cline{2-10}  & \multicolumn{3}{c}{**C/N0 Dependent**} & \multicolumn{3}{c}{**SISRE Based**} & \multicolumn{3}{c}{**SPP**} \\ \cline{2-10}  & **E (m)** & **N (m)** & **U (m)** & **E (m)** & **N (m)** & **U (m)** & **E (m)** & **N (m)** & **U (m)** \\ \hline SF 1-G & 1.09 & 1.49 & 2.37 & & & 3.47 & 4.54 & 8.74 & 94.8 \\ SF-GE & 1.07 & 1.32 & 2.73 & 1.50 & 2.12 & 2.91 & 3.04 & 3.91 & 7.84 & 96.8 \\ SF-GEJ & 0.62 & 1.25 & 2.56 & 1.76 & 2.88 & 3.23 & 2.97 & 3.70 & 7.55 & 97.3 \\ SF-GEJ C 2 & 0.95 & 1.98 & 3.29 & 1.37 & 2.49 & 3.12 & 3.02 & 3.82 & 7.38 & 98.0 \\ SF-GEJ C without GEO & 0.45 & 1.24 & 2.60 & 1.11 & 2.26 & 3.14 & 3.06 & 3.80 & 7.70 & 97.7 \\ DF 3-G & 0.67 & 0.92 & 1.64 & & & 2.62 & 3.46 & 7.37 & 97.9 \\ DF-GE & 0.67 & 0.87 & 1.48 & 0.77 & 1.76 & 1.87 & 2.18 & 2.95 & 6.53 & 99.3 \\ DF-GEJ & 0.66 & 1.07 & 1.70 & 0.82 & 1.54 & 1.96 & 4.62 & 4.45 & 9.87 & 89.1 \\ DF-GEJ & 0.62 & 0.83 & 1.45 & 0.80 & 1.84 & 1.97 & 2.10 & 2.66 & 6.17 & 99.6 \\ DF-GEJ(IONO-FREE) & 1.71 & 2.04 & 1.63 & 1.69 & 2.85 & 2.04 & 5.17 & 5.32 & 8.67 & 63.5 \\ DF-GEJ & 0.84 & 1.62 & 1.46 & 0.85 & 1.94 & 1.84 & 2.15 & 2.68 & 6.18 & 99.7 \\ DF-GEJC without GEO & 0.61 & 0.92 & 1.40 & 0.73 & 1.84 & 1.84 & 2.19 & 2.68 & 6.21 & 99.7 \\ \hline \hline \end{tabular}  
* SF means only single frequency L1/E1 measurements are used for positioning; 2 CEJC represent GPS/Galileo/ QZSS/BeiDou, Separately. 3 DF means dual-frequency L1/E1 and L5/E5 measurements are used for positioning.  
\end{table} 
Table 4: RMS of TD filter and SPP solutions for Xiaomi Mi 8 in static test. Figure 15: Positioning errors of double frequency TD filter and SPP solutions for Xiaomi Mi 8 in open-sky rooftop situations. The horizontal position scatters are shown in the odd columns, while the vertical scatters are shown in the even columns. The concentric ellipses or straight lines inside each panel denote the 2\(\sigma\) domain of the scatters. ‘GE(L1+L5)’ indicates the positioning results using Galileo and those GPS satellites with L5 measurements. ‘GEJ(IONO-FREE)’ is the positioning results with the dual-frequency ionosphere-free combined GPS, Galileo, and QZSS measurements. ‘No GEO’ means the positioning results are generated by excluding Beidou GEO satellites. only the Galileo and those GPS satellites with L5 measurements, the time differenced filter algorithm positioning error is 0.66 m, 1.07 m, and 1.70 m in E, N, and U directions, respectively, which is slightly worse than the positioning results with all Galileo and GPS satellites. The SPP positioning error increased to 4.62 m, 4.45 m, and 9.87 m, and the SPP availability decreased to 89.1%. Clearly, as only a subset of GPS satellites transmits L5 signals, if use only Galileo satellites and those GPS satellites with L5, the number of usable satellites rapidly reduced and the navigation performance degraded.