# Precise Point Positioning Using Dual-Frequency GNSS Observations on Smartphone
## 3 Experiments and Results
### Kinematic Data Analysis  
The kinematic data was collected on the playground of Jilin University on October 16, 2018 (DOY 228 14:09-14:13 UTC). The surrounding environment of the station is shown in Figure 7. The test was carried out along the runway track using a Mi 8 smartphone and a Hi-target geodetic GNSS receiver by means of a pedestrianly hand-held approach. The \"real track\" is the positioning result of geodetic receiver GPS L1/L2, Galileo E1/E5a observation data processed by RTKLIB PPP kinematic mode. In addition, the horizontal position errors \(d_{i}\) are defined as the distances between \"real track\" and other tracks derived from four data sets using the following formula:  
\[d_{i}=\sqrt{\Delta E_{i}^{2}+\Delta N_{i}^{2}} \tag{43}\]  
where \(\Delta E_{i}\) and \(\Delta N_{i}\) can be calculated from Equations (37) and (38). According to the data processing strategies in Table 1, the same four data sets in the previous section were processed in kinematic PPP mode. Figure 8 showed the horizontal position errors of four data sets in kinematic. The tracks of receiver data sets were slightly different from the real track,  
Figure 7: Kinematic positioning track in Google Earth. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Satellite** & **STD of Smartphone Carrier Phase Residual** & **STD of Receiver Carrier Phase Residual** \\ \hline G03 & N/A & 0.009 \\ G08 & 0.073 & 0.010 \\ G09 & 0.045 & 0.010 \\ G10 & 0.032 & 0.008 \\ G24 & 0.056 & 0.016 \\ G25 & 0.051 & 0.008 \\ G26 & 0.030 & 0.007 \\ G27 & 0.032 & 0.007 \\ G32 & 0.039 & 0.007 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Standard deviation of carrier phase residuals of smartphone and receiver (m). the \"receiver dual-frequency\" track was in good agreement with the real track, and the \"receiver single-frequency\" had an offset of approximately 1 m. The \"smartphone dual-frequency\" track had severe fluctuations within 4-5 m of the actual track with extreme offsets over 20 m, and the \"smartphone single-frequency\" track had an overall offset of 3-5 m.  
In the kinematic mode, the positioning results of the receiver data sets were better than those of the smartphone data sets. 12 satellites of different satellite systems were selected in Figure 9, and the mean and STD of \(C/N_{0}\) are summarized in Table 6. The smartphone \(C/N_{0}\) (carrier-to-noise ratio) was approximately 10-15 dB-Hz lower than that of the receiver, indicating a poorer data quality due to the relatively larger observation noise of smartphone. The number of satellites observed by the smartphone was about 25, 15 of which were applied in single-frequency positioning, and 5 of which were applied in dual-frequency positioning. Although the antenna of the smartphone tracked many satellites, half of them could not be processed due to the low-quality data and low elevation angle (Figure 10). The track of \"smartphone dual-frequency\" was unstable compared to that of \"smartphone single-frequency\". The observed number of satellites of the former was much lower than that of the latter. The large number of observed satellites of the \"smartphone single-frequency\" indicates relatively stable positioning results, and the lower number of observed satellites of \"smartphone dual-frequency\" indicates a small number of ionosphere-free observations, making it very difficult to get relatively stable and accurate positioning results.