# Relative Positioning in Remote Areas Using a GNSS Dual Frequency Smartphone
## 4 Results
### Test 5  
Figure 17 and Table 13 show the results obtained during Test 5 for the Galileo + GPS combination using smartphone A in pillar 5 (Figure 1), for three hours of observation. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**CASC**} & \multicolumn{3}{c}{**CEUT**} & \multicolumn{3}{c}{**GAIA**} & \multicolumn{3}{c}{**VIGO**} \\ \cline{2-13}  & **E** & **N** & **U** & **E** & **N** & **U** & **E** & **N** & **U** & **E** & **N** & **U** \\ \hline \multirow{3}{*}{Mi8} & AVE & 0.087 & \(-\)0.013 & \(-\)0.160 & 0.048 & \(-\)0.122 & \(-\)0.059 & 0.062 & 0.003 & \(-\)0.097 & 0.082 & 0.072 & \(-\)0.074 \\  & STD & 0.121 & 0.112 & 0.229 & 0.036 & 0.325 & 0.362 & 0.092 & 0.018 & 0.091 & 0.064 & 0.051 & 0.049 \\  & RMS & 0.132 & 0.092 & 0.246 & 0.057 & 0.292 & 0.301 & 0.097 & 0.015 & 0.122 & 0.097 & 0.083 & 0.085 \\ \hline \multirow{3}{*}{PolaRx5} & AVE & \(-\)0.047 & \(-\)0.213 & 0.244 & \(-\)0.043 & \(-\)0.173 & \(-\)0.053 & 0.000 & \(-\)0.003 & 0.008 & \(-\)0.009 & 0.067 & 0.025 \\  & STD & 0.105 & 0.050 & 0.169 & 0.116 & 0.235 & 0.182 & 0.009 & 0.019 & 0.044 & 0.007 & 0.005 & 0.057 \\ \cline{1-1}  & RMS & 0.098 & 0.216 & 0.280 & 0.104 & 0.258 & 0.158 & 0.007 & 0.015 & 0.037 & 0.011 & 0.067 & 0.053 \\ \hline \end{tabular}
\end{table} 
Table 11: Smartphone and receiver statistics at Test 3. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**CASC**} & \multicolumn{3}{c}{**CEUT**} & \multicolumn{3}{c}{**GAIA**} & \multicolumn{3}{c}{**VIGO**} \\ \cline{2-13}  & **E** & **N** & **U** & **E** & **N** & **U** & **E** & **N** & **U** & **E** & **N** & **U** \\ \hline AVE & 0.078 & \(-\)0.033 & 0.092 & 0.005 & \(-\)0.396 & \(-\)0.392 & \(-\)0.220 & \(-\)0.117 & \(-\)0.058 & 0.002 & \(-\)0.083 & 0.045 \\ STD & 0.054 & 0.026 & 0.079 & 0.140 & 0.194 & 0.186 & 0.008 & 0.005 & 0.021 & 0.048 & 0.054 & 0.068 \\ RMS & 0.018 & 0.004 & 0.030 & 0.020 & 0.194 & 0.188 & 0.048 & 0.014 & 0.004 & 0.002 & 0.010 & 0.007 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Statistics results from the Test 4. The Test 6 results show accuracies similar to those obtained in the other tests, with values below 20 cm for the CEUT station, while using the other CORS stations we obtained accuracies below 10 cm for most components. These results are no better than Test 5, despite the longer observation time. This may be due to the smaller number of Galileo satellites tracked by the smartphone, as shown in Figure 5e,f). A drop in the number of Galileo satellites tracked after the first part of the experiment also contributed to this result. Looking at the satellites tracked by the Alloy receiver (see Figure 5f), we notice that the number of Galileo satellites has not decreased as drastically, so the issue is related to the smartphone's tracking capabilities. The tests performed showed consistent results for differential positioning using long baselines, and, as expected, the smartphone positioning performance was worse in the case of the farthest CEUT station, but still with very good values, below 30 cm. We can conclude that using a smartphone with dual frequency measurements we can still get quite good results, revealing the potential of these low-cost GNSS devices for application in differential positioning based on distant reference stations, with a tendency to improve its performance with the completion of the Galileo constellation and the modernization of the GPS constellation. It is important to understand whether similar performances can be expected elsewhere across the globe. GNSS signals are affected by atmospheric, ionosphere, and troposphere delays, which can be minimized or even eliminated by applying relative positioning techniques in the case of short baselines, as receivers are subject to similar effects. For our work, we expect ionospheric conditions to be the limiting factor for accuracy, in particular, because an ionosphere-free dual frequency combination could not be used for many of the GPS satellites.