## 3 Results
### Velocity Domain Results
The solutions obtained using Galileo measurements from the uBlox receiver, panel (f), are very similar to the GPS case with the same device, resulting in fewer and smaller anomalous error peaks. For Galileo with Xiaomi, panel (g), the TDCP solution is impossible to estimate due to an insufficient number of measurements during the session, while the Doppler solution is possible only in the second part of the session, with degraded performance (rms errors of about 1 m/s) due to the probable presence of anomalous measurements. Considering BeiDou measurements from the uBlox device, panel (h), both Doppler and TDCP are degraded in the initial part of the session because of poor geometry, while in the remaining part, velocity errors are prevalently below 20 cm/s for the Doppler case and 3 cm/s for TDCP case. A large spike is evident in the TDCP solution, related to anomalous measurements. Considering BeiDou measurements from Xiaomi, panel (i), the poor geometry issue in the initial part of the session is not present, but several spikes are present in the TDCP solution. The Doppler velocity estimation seems to be better than the uBlox case, with more bounded errors. The mean, root mean square (rms), and maximum horizontal and vertical velocity errors are computed and summarized in Tables 4 and 5, respectively. Comparing the single GNSS configurations in terms of the considered figures of merit, it is evident that the best performance is obtained by the high-grade device. For uBlox, GPS-only performance and Galileo-only performance are similar, with the Doppler solution prevailing for GPS and the TDCP solution prevailing for Galileo. The GPS-only solution with Xiaomi demonstrates good performance, better than the corresponding uBlox \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Novatel**} & \multicolumn{3}{c}{**uBlox**} & \multicolumn{3}{c}{**Xiaomi**} \\ \hline  & & **Mean** & **rms** & **Max** & **Mean** & **rms** & **Max** & **Mean** & **rms** & **Max** \\ \hline \multirow{2}{*}{**GPS**} & Doppler & 0.018 & 0.020 & 0.072 & 0.027 & 0.032 & 0.173 & 0.009 & 0.013 & 0.232 \\  & TDCP & 0.002 & 0.002 & 0.017 & 0.005 & 0.031 & 0.959 & 0.006 & 0.007 & 0.100 \\ \hline \multirow{2}{*}{**GLO**} & Doppler & - & - & - & 0.153 & 0.288 & 2.411 & 0.039 & 0.045 & 0.545 \\  & TDCP & - & - & - & 0.056 & 0.205 & 7.062 & 0.100 & 1.687 & 31.908 \\ \hline \multirow{2}{*}{**GAL**} & Doppler & - & - & - & 0.035 & 0.042 & 0.187 & 0.675 & 0.916 & 3.674 \\  & TDCP & - & - & - & 0.003 & 0.009 & 0.341 & - & - & - \\ \hline \multirow{2}{*}{**BDS**} & Doppler & - & - & - & 0.108 & 0.149 & 1.234 & 0.044 & 0.058 & 1.175 \\  & TDCP & - & - & - & 0.012 & 0.027 & 1.201 & 0.023 & 0.032 & 0.450 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Horizontal velocity error (m/s): mean, root mean square, and maximum errors for single devices and single GNSSs. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Novatel**} & \multicolumn{3}{c}{**uBlox**} & \multicolumn{3}{c}{**Xiaomi**} \\ \hline  & & **Mean** & **rms** & **Max** & **Mean** & **rms** & **Max** & **Mean** & **rms** & **Max** \\ \hline \multirow{2}{*}{**GPS**} & Doppler & 0.029 & 0.036 & 0.117 & 0.042 & 0.054 & 0.283 & 0.031 & 0.045 & 0.781 \\  & TDCP & 0.003 & 0.004 & 0.055 & 0.010 & 0.065 & 1.795 & 0.009 & 0.017 & 0.356 \\ \hline \multirow{2}{*}{**GLO**} & Doppler & - & - & - & 0.196 & 0.385 & 3.532 & 0.112 & 0.131 & 1.376 \\  & TDCP & - & - & - & 0.078 & 0.288 & 9.764 & 0.105 & 1.673 & 32.439 \\ \hline \multirow{2}{*}{**GAL**} & Doppler & - & - & - & 0.045 & 0.057 & 0.318 & 0.825 & 1.053 & 3.523 \\  & TDCP & - & - & - & 0.005 & 0.023 & 0.887 & - & - & - \\ \hline \multirow{2}{*}{**BDS**} & Doppler & - & - & - & 0.110 & 0.170 & 1.728 & 0.076 & 0.089 & 0.639 \\  & TDCP & - & - & - & 0.013 & 0.031 & 1.309 & 0.024 & 0.036 & 0.499 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Vertical velocity error (m/s): mean, root mean square, and maximum errors for single devices and single GNSSs.