## 4 Performance Assessment of Single Point Positioning with Smartphone Code Pseudoranges
### Galileo Standalone Positioning: E5a versus the E1-Based Solution  
The next analysis aims to verify if the positioning with the E5a code observations outperforms that with E1 ones as the former signals are of lower noise than the latter (cf. Table 2). To this end, we compare between the single point positioning results obtained using Galileo signals on the E1 and E5a frequency bands for the Xiaomi Mi 9 smartphone.  
In Figure 14, the three-dimensional positioning error comparison between E1 (left panel, red color) and E5a signals (right panel, blue color) of Xiaomi Mi 9 is shown. Figure 15 shows the corresponding three-dimensional position error histogram in the same color scheme. Each bin is 1 m wide. Both figures immediately point out how the accuracy obtained using the signals on the E5a frequency is higher than that obtained using the signals on E1. The blue curve (E5a error) is narrower than the red one (E1) in the histograms given in Figure 15. This conclusion is confirmed by the statistics given in Table 5. The table reveals that 3D-RMS is 14.34 m for Galileo single point positioning with E1 signals with respect to 7.91 m in the case of an E5a-based solution: the use of pseudoranges on E5a instead of the E1 frequency band led to a halving of the three-dimensional error.  
The improvement in position accuracy obtained using the E5a instead of the E1 code observations is also evident by separating the horizontal component of the error from the vertical one as showed in Figure 16. The horizontal error scatter plot and the vertical error time series are shown in the left and the right panels, respectively. The horizontal accuracy expressed in terms of root mean square of the horizontal error is of 8.44 m and 3.17 m for E1 and E5a-based SPP solutions, respectively (Table 5). With regard to vertical accuracy, the results confirmed the best performance of SPP with E5a observations with a RMS of the vertical component of 7.24 m compared to the 11.60 m of E1-SPP. The results are a confirmation of what is highlighted in the observation assessment section where we showed that, for the analyzed smartphones, the noise on the E5a is lower than that on the E1. These results are also coherent with the findings of [PERSON] et al. (2018), who attributed the better performance the E5a-based positioning as compared to the E1-based one, to the reduction of the multipath error.  
Figure 16: Horizontal and vertical coordinate component error scatter plots for Galileo single point positioning of Xiaomi Mi 9. Red markers represent an E1-based solution, while blue ones correspond to the E5a-based solution.  
Figure 15: Three-dimensional coordinate error histogram for Galileo single point positioning of Xiaomi Mi 9. The results achieved with with E1 code observations are represented in red while those obtained with E5a ones are represented in blue. Each bin is 1 m wide.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**North**} & \multicolumn{2}{c}{**East**} & \multicolumn{2}{c}{**Up**} & \multicolumn{2}{c}{**Hor.**} & \multicolumn{1}{c}{**Ver.**} & \multicolumn{1}{c}{**3D**} \\ \cline{2-10}
**Signal** & **Mean** & **STD** & **Mean** & **STD** & **Mean** & **STD** & **RMS** & **RMS** & **RMS** \\  & **[m]** & **[m]** & **[m]** & **[m]** & **[m]** & **[m]** & **[m]** & **[m]** & **[m]** \\ \hline E1 & 4.03 & 5.92 & 0.84 & 4.37 & 1.70 & 11.47 & 8.44 & 11.60 & 14.34 \\ E5a & 0.82 & 2.71 & \(-\)0.10 & 1.43 & 5.21 & 5.04 & 3.17 & 7.24 & 7.91 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Coordinate statistics of Galileo E1 versus E5a-based single point positioning for Xiaomi Mi 9.