# Real-time Precise Point Positioning with a Xiaomi MI 8 Android Smartphone
## 5 Results  
Using the method described in Section 3, calculating the RMS of pseudorange observations of each mobile phone, the results are shown in Table 2 below. Table 3 shows each device's RMS of carrier phase observation change rates. The average RMS of carrier phase observation change rates of Huawei Honor 9, Huawei P10, and Xiaomi MI 8 mobile phone are 5.5, 6.4 and 4.0 times of the geodetic receiver, respectively. Tables 2 and 3 show that the quality of the raw observations of Xiaomi MI 8 is obviously improved compare with single-frequency mobile phones. \begin{table}
\begin{tabular}{c c} \hline \hline
**Setting Items** & **Details** \\ \hline Observations used Satellite orbit errors and clock biases Ionospheric delay errors & Single-frequency pseudorange and carrier phase Precise predicting orbit and clock bias files Predicting ionospheric grid files Correcting with the Hopfield model [16; 18] and the remainder is estimated as a parameter Effects of relativity and earth rotation Correcting with the corresponding formula [19] Weighting method Satellite elevation angle Integer ambiguities of carrier phase & Estimating float solution Cutoff satellite elevation angle 10\({}^{\circ}\) Parameters estimation method Standard static Kalman filter \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The detailed settings of the precise point positioning (PPP) method used. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Devices**} & \multicolumn{6}{c}{**RMS of Pseudorange Observations (m)**} \\ \cline{2-7}  & **Average** & **GPS P1** & **GPS P5** & **Galileo P1** & **Galileo P5** & **BDS** & **GLONASS** \\ \hline Huawei Honor 9 & 12.23 & 10.96 & \(\backslash\) & \(\backslash\) & \(\backslash\) & 10.96 & 14.83 \\ Huawei P10 & 8.58 & 8.11 & \(\backslash\) & 7.39 & \(\backslash\) & 8.11 & 12.57 \\ Xiaomi MI 8 & 3.97 & 3.59 & 2.05 & 2.92 & 1.78 & 3.26 & 8.28 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The RMS of pseudorange observations of each mobile phone with different global navigation satellite systems (GNSS), where P1 and P5 denote pseudorange observations of two frequencies L1/E1 and L5/E5. In the three data collection processes, the number of GPS, BDS, and GLONASS satellites that can be observed by smartphones is relatively stable, 6-8 for GPS, 6-7 for BDS; but the number of Galileo satellites observed is small, 3 for Huawei P10 and 0 for Huawei Honor 9, while the Xiaomi MI 8 observed 3 in the third dataset collection process, only 1 in the second dataset collection process. In addition, the observed GPS satellites with L5 signal are 2-3. Too few observed satellites with L5/E5 signals has resulted in inefficient use of L5/E5 frequency data, and thus positioning tests in this work are all use single frequency observations. Using the PPP method detailed in Section 3, positioning tests was performed with a Xiaomi 8 smartphone. In order to evaluate the impact of using different constellation combinations on the positioning results, we used a variety of GNSS systems combinations for testing. The RMS positioning errors of representative GNSS system combinations are shown in Table 4. In general, as the number of constellations used increases, the positioning performance gradually improves. There are 6 parameters that need to be estimated in our positioning strategy (when using single GNSS system data), and the number of satellites observed of GPS/BDS systems is 6-8, which results in little or no redundant observations. Thus, the performance of single constellation positioning is poor. Thanks to the number of observable GPS and BDS satellites, the result using GPS and BDS data is obviously better than using single constellation data. Since the number of Galileo satellites observed by mobile phones is small, the positioning performance is not obviously improved after adding Galileo data. For GLONASS, after adding the its data, the positioning performance of some time periods can be improved, and some time periods (the 1 st and 5 th time periods) are badly affected.