# Relative Positioning in Remote Areas Using a GNSS Dual Frequency Smartphone
## 3 Satellite Visibility and Observed Signals
### Signal Quality  
The SNR is a very relevant parameter to characterize the quality of the acquired measurements, depending on the tracking, antenna, and bandwidth parameters of the GNSS receiver front-end. In the case of smartphones' low-cost antennas, their linear polarization, as well as the lower quality front-end, results in a low signal gain. However, SNR can also be affected by other factors such as low satellite signals, malicious interference (jamming), or unintentional interference such as signal obstruction or multipath, which in the smartphone has a low suppression. To mitigate the effect of some of these issues, the observations were made in an open space with good sky visibility and a 15\({}^{\circ}\) elevation mask was considered in processing. The analysis of the SNR of all devices used was performed for the Galileo and GPS signals, E1, L1, E5a, and L5, as shown in the plots at Figures 6-9, where each color represents a satellite. The statistical parameters average (AVE), standard deviation (STD), minimum (MIN), and maximum (MAX) are presented in Tables 3-5. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Flight Mode**} & \multicolumn{5}{c}{**Smartphone A**} & \multicolumn{5}{c}{**Smartphone B**} \\ \cline{2-10}  & **E1** & **L1** & **E5a** & **L5** & **E1** & **L1** & **E5a** & **L5** \\ \hline \multirow{4}{*}{ON} & AVE & 29.6 & 31.6 & 29.2 & 29.2 & 30.7 & 32.1 & 28.0 & 31.3 \\  & STD & 3.1 & 3.9 & 4.1 & 4.8 & 3.1 & 4.4 & 3.5 & 4.5 \\  & MIN & 14.2 & 12.3 & 17.0 & 17.0 & 15.8 & 12.9 & 17.0 & 17.0 \\  & MAX & 36.3 & 40.2 & 35.1 & 37.0 & 37.9 & 41.7 & 36.3 & 37.7 \\ \hline \multirow{4}{*}{OFF} & AVE & 30.2 & 30.7 & 28.1 & 31.0 & 31.6 & 32.3 & 27.6 & 30.7 \\  & STD & 3.0 & 4.5 & 4.4 & 4.8 & 3.5 & 3.5 & 4.0 & 4.1 \\ \cline{1-1}  & MIN & 16.6 & 12.0 & 17.0 & 17.0 & 13.9 & 12.2 & 17.0 & 17.0 \\ \cline{1-1}  & MAX & 37.6 & 40.9 & 36.5 & 38.7 & 37.7 & 40.4 & 35.7 & 38.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Test 1 SNR statistics for smartphone A and B (units: dbHz). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Smartphone A**} & \multicolumn{5}{c}{**Smartphone B**} \\ \cline{2-10}  & **E1** & **L1** & **E5a** & **L5** & **E1** & **L1** & **E5a** & **L5** \\ \hline AVE & 38.6 & 37.9 & 34.3 & 34.8 & 46.3 & 44.3 & 46.3 & 46.4 \\ STD & 4.9 & 6.3 & 4.3 & 5.2 & 5.1 & 5.3 & 5.2 & 5.6 \\ MIN & 17.9 & 11.4 & 17.0 & 17.0 & 24.8 & 23.8 & 24.9 & 24.7 \\ MAX & 46.1 & 48.3 & 40.8 & 42.8 & 52.6 & 51.2 & 52.3 & 54.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Test 2 SNR statistics for smartphone A and Alloy receiver (units: dbHz). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{5}{c}{**Smartphone A**} & \multicolumn{5}{c}{**PolaRx5**} \\ \cline{2-10}  & **E1** & **L1** & **E5a** & **L5** & **E1** & **L1** & **E5a** & **L5** \\ \hline AVE & 36.2 & 39.6 & 31.3 & 33.7 & 40.8 & 44.2 & 43.1 & 47.3 \\ STD & 3.3 & 3.8 & 4.9 & 3.9 & 5.4 & 6.1 & 5.2 & 5.9 \\ MIN & 20.9 & 14.2 & 17.3 & 17.1 & 18.0 & 18.0 & 11.2 & 22.6 \\ MAX & 43.4 & 46.9 & 41.8 & 39.6 & 48.0 & 51.3 & 50.4 & 54.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Test 3 SNR statistics for smartphone A and PolaR5 receiver (units: dbHz). Figure 6: Test 1 SNR smartphone A: E1 flight mode on (**a**); L1 flight mode off (**b**); E5a flight mode on (**c**); L5 flight mode on (**d**); E1 flight mode off (**e**); L1 flight mode off (**f**); E5a flight mode off (**g**); L5 flight mode off (**h**). Figure 7: Test 1 SNR smartphone B: E1 flight mode on (**a**); L1 flight mode off (**b**); E5a flight mode on (**c**); L5 flight mode on (**d**); E1 flight mode off (**e**); L1 flight mode off (**f**); E5a flight mode off (**g**); L5 flight mode off (**h**). Figure 8: Test 2 SNR: E1 smartphone (**a**) and receiver (**b**); L1 smartphone (**c**) and receiver (**d**); E5a smartphone (**e**) and receiver (**f**); L5 smartphone (**g**) and receiver (**h**).