# Real-Time Geophysical Applications with Android GNSS Raw Measurements
## 3 Results
### Ionospheric Analysis  
For the ionopsheric analysis, a static acquisition using the Xiaomi Mi8 during 15 min was considered. In order to validate the Xiaomi Mi8 results, the M0 SE GNSS permanent station was used as reference. In this case, the distance between the smartphone and M0 SE was 107.58 m, so we could assume that we were referring to the same ionospheric condition. Figure 11 shows the trend of \(\Delta sTEC/\Delta t\) with respect to GPS satellite G24 for M0 SE and for Xiaomi Mi8 during the 15 min of acquisition. It is possible to observe that the Xiaomi Mi8 \(\Delta sTEC/\Delta t\) series was much noisier than that of M0 SE: the RMSEs for G24 \(\Delta sTEC/\Delta t\) were 0.011 TECU/s and 0.066 TECU/s, respectively, for M0 SE and Xiaomi Mi8. Hence, a moving median on window of 5-10-15-20-30 s was computed in order to clean the noisy data and try to detect some kind of ionospheric disturbances, if they were present. The median operator was chosen since it is much more robust to outliers compared to the mean. Then, RMSEs on the median series were computed and compared to those of M0 SE. Already using the median with a window of 15 s, results comparable with the M0 SE results were obtained as shown in Table 4. Figure 12 shows the original Xiaomi Mi8 \(\Delta sTEC/\Delta t\) series and the one after using a 10 s window moving median. It is important to highlight how the noise was remarkably decreased just by using a 10 s window moving median, which had no influence of any ionospheric perturbation detection.  
The same analysis was carried out on Galileo satellite E13. Figure 13 shows the trend of \(\Delta sTEC/\Delta t\) with respect to Galileo satellite E13 for M0 SE and for Xiaomi Mi8 during the 15 min of acquisition. Also in this case, it is possible to observe that the Xiaomi Mi8 \(\Delta sTEC/\Delta t\) series (RMSE: 0.066 TECU/s) was much noisier than that of M0 SE (RMSE: 0.013 TECU/s); thus, the same procedure was applied. Table 5 shows the RMSEs for the different time windows used for the moving median. A window of 10 s allowed a noise comparable to that of M0 SE to be obtained. Figure 14 shows the original Xiaomi Mi8 \(\Delta sTEC/\Delta t\) series and the one after using a 10 s window moving median. Also in this case, the 10 s window moving median allowed the noise to be notably reduced.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & \multicolumn{5}{c}{**RMSE (TECU/s)**} \\ \hline  & **5 s** & **10 s** & **15 s** & **20 s** & **30 s** \\ \hline
**Xiaomi Mi 8** & 0.027 & 0.017 & 0.014 & 0.011 & 0.010 \\ \hline \hline \end{tabular}
\end{table}
Table 4: RMSEs of Xiaomi Mi8 moving median series for satellite G24 for different time windows.  
Figure 11: The trend of \(\Delta sTEC/\Delta t\) with respect to GPS satellite G24 for M0 SE and for Xiaomi Mi8 are respectively depicted in blue and red.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Mean** & **Std** & **RMSE** \\ \hline
**1D Velocity (m/s)** & 0.000 & 0.011 & 0.011 \\
**1D Displacements (m)** & \(-\)0.014 & 0.015 & 0.021 \\ \hline \hline \end{tabular}
\end{table}
Table 3: RMSEs for residual 1D velocity and displacements.  
Figure 14: The trends of the original E13 Xiaomi Mi8 \(\Delta sTEC/\Delta t\) series and after using a 10 s window moving median are respectively depicted in red and black.  
Figure 12: Trends of the original G24 Xiaomi Mi8 \(\Delta sTEC/\Delta t\) series and of the one after using a 10 s window moving median depicted respectively in red and black.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{5}{c}{**RMSE (TECU/s)**} \\ \hline  & **5 s** & **10 s** & **15 s** & **20 s** & **30 s** \\ \hline
**Xiaomi Mi \$** & 0.019 & 0.011 & 0.010 & 0.008 & 0.007 \\ \hline \hline \end{tabular}
\end{table}
Table 5: RMSEs of Xiaomi Mi8 moving median series for satellite E13 for different time windows.  
Figure 13: The trends of \(\Delta sTEC/\Delta t\) with respect to Galileo satellite E13 for M0 SE and for Xiaomi Mi8 are respectively depicted in blue and red.