## 3 Data Processing and Analysis for Smartphone Real-Time Kinematic (RTK) Positioning
### Analysis of RTK-Positioning Convergence Time by Segment  
To verify the consistency of the convergence time in different periods, we solved the entire observation data in segments, that is, we reinitialised the coordinates and ambiguity parameters in a segments once every 1 h, and then solved the segments separately. As reported above, the combination G/E/C of single-frequency observations provides the best convergence overall. Thus, we used it for data processing without resolving the BDS ambiguity. The other calculation parameters were set as listed in Table 2. Considering slow convergence, we started to fix the ambiguity after 3 min of observations. In addition to the data from 15 November 2020, which were used above, we used two additional datasets collected in recent days, at the same location and with a similar setup. The data collected on 11 November 2020 are approximately of 3 h, and the data collected on 14 November 2020 are approximately of 5 h. Here, we used the last 3 h of the \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \begin{tabular}{c} **Observation** \\ **Combination** \\ \end{tabular} & \begin{tabular}{c} **Mean Number** \\ **of Satellites** \\ \end{tabular} & \begin{tabular}{c} **Fixing Rate** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} **Error-Fixing** \\ **Rate (\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Convergence** \\ **Time (min)** \\ \end{tabular} &
\begin{tabular}{c} **RMS Error after Convergence** \\ **East (m)** \\ \end{tabular} \\ \hline G L1/L5 & 2.9 & 22.4 & 5.4 & Non-convergent & – & – & – \\ G L1/L5 (float L5) & 2.9 & 59.1 & 20.4 & Non-convergent & – & – & – \\ G L1/L5 + E E1/E5a & 5.8 & 10.6 & 8.7 & Non-convergent & – & – & – \\ G L1/L5 + E1/E5a & 88.0 & 3.6 & 30.8 & 0.013 & 0.011 & 0.024 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Solutions of dual-frequency combinations. The mean number of satellites only includes dual-frequency satellites. Figure 12: Accuracy of fixed solutions compared with corresponding float solutions. 5 h data for analysis, owing to the clock jump in the previous data, and it will not affect the results of the segmented solution. These two datasets mainly aim to increase the amount of data for convergence time analysis and do not consider the impact of geomagnetic storm conditions on different days. Figure 13 shows the segmented solutions for 1 h intervals. Table 8 lists the convergence time of each session, the mean number of satellites in combination G/E (as BDS is not fixed, the number of BDS satellites is not considered), and the mean number of candidate ambiguities that meet the fixed conditions (e.g., C/N0 threshold, cycle slip). The convergence time differs across segments, mostly being 10-20 min and exceeding 30 min for few segments. In addition, the ambiguity can hardly be resolved for two segments mainly because the number of candidate ambiguities is very small. The corresponding segment with a long convergence time usually has few candidate ambiguities. For example, for segment 1 of dataset 2, the number of candidates is the largest, achieving the fastest convergence, whereas for segment 3 of dataset 2 and segment 1 of dataset 3, the number of candidates is lower than 1 (0.4 and 0.2, respectively), and the ambiguity cannot be fixed. Even if the total number of satellites is large, when a satellite elevation and C/N0 are very low or a cycle slip occurs, the corresponding ambiguity does not meet the fixed conditions and cannot be used for ambiguity resolution, resulting in few candidate ambiguities. On the other hand, the results in Section 3.3 show that simply including the number of observations from other constellations or frequencies in ambiguity resolution is not conducive to a higher fixing rate. Figure 13: Results of segmented solutions over 1 h intervals for data acquired over 3 days. (**a**) Dataset 1 collected on 15 November 2020, (**b**) dataset 2 collected on 11 November 2020, and (**c**) dataset 3 collected on 14 November 2020.