## 6 Discussion and Summary  
In the conducted GNSS measurements, a mobile phone was used with the option of data recording on two frequencies, L1/E1 and L5/E5a, and a possibility of registering GNSS observations from GPS and GALILEO systems, and L1 observations for the GLONASS system. This created a possibility to track over 25 satellites simultaneously during the test measurements, of which more than 10 satellites had observations on L1/E1-L5/E5a. Unfortunately, GALILEO observations were not recorded at the reference station. Therefore, only L1 frequency observations for the GPS system were used for comparative calculations in the described tests. In addition, GPS plus GLONASS calculations were made, but no better results were obtained than with GPS-only. Generally, some centimeters accuracy was obtained at the level of the professional geodetic receiver for 30 min sessions, and in some cases, for 10 min sessions. This means that, undoubtedly, a new era has arrived for GNSS systems, where every mobile phone user will have the opportunity to obtain a position with some centimeters accuracy. What is more, mobile phone manufacturers even overtook the owners of reference station systems by providing L1-L5 observations from the GALILEO system. This creates much greater positioning options, both for autonomous positioning, as well as for static measurements or RTK techniques. Figure 23 shows time series of residual values of float DD ambiguities (N1), including code observations P(L1) and P(L5), for the baselines of OPNT-JAVAD and OPNT-Huawei P30. The standard  
Figure 22: Huawei P30 Pro skyplot of GPS-only (third experiment). \begin{table}
\begin{tabular}{c c c c} \hline
**Minutes** & **dx (m)** & **dy (m)** & **dh (m)** \\ \hline
0–30 & 0.003 & 0.016 & \(-\)0.001 \\ \hline
30–60 & \(-\)0.011 & 0.009 & \(-\)0.042 \\ \hline min & \(-\)0.011 & 0.009 & \(-\)0.042 \\ \hline max & 0.003 & 0.016 & \(-\)0.001 \\ \hline SD & 0.010 & 0.005 & 0.029 \\ \hline \end{tabular}
\end{table} 
Table 14: 30 min sub-session positioning results summary, baseline OPNT–P30 Pro (4 km). \begin{table}
\begin{tabular}{c c c c} \hline
**Minutes** & **dx (m)** & **dy (m)** & **dh (m)** \\ \hline
0–60 & \(-\)0.001 & 0.016 & \(-\)0.008 \\ \hline \end{tabular}
\end{table} 
Table 15: 60 min session positioning results summary, baseline OPNT–P30 Pro (4 km). deviation (SD) for the P(L1) code measurements was 2.6 m for the Huawei P30 Pro and 0.8 m for the JAVAD receiver, while for the P(L5) code, it was 0.8 and 0.5 m, respectively. It can be seen that if the L1 code measurements are inferior to the Javad GNSS receiver, the P(L5) code measurements are at a similar level of accuracy, only slightly differing from the professional GNSS receiver used. This creates great opportunities in the future for the use of smartphones based on the P(L5) code. Based on this information, this code should and probably will be mainly used for GNSS positioning, enabling even decimeter accuracy of autonomous positioning. In addition, such high accuracy of the P(L5) code definitely increases the possibilities for determining ambiguities for single observation epochs of phase observations L1/E1-L5/E5a of GPS and GALILEO systems. However, it should be noted that the phase observations L1-L5 are currently much worse for the tested Huawei P30 pro compared to those of a professional GNSS receiver. The ambiguity values for N1-N5 solutions from single measurement epochs based on the use of only one pair of G06-G26 satellites are shown in Figure 24. For the OPNT-Javad baseline, we have all float ambiguities arranged precisely along the x-axis, while for the OPNT-Huawei P30 Pro baseline, it can be seen that some phase observations have errors that can be understood as gross errors. However, many of the ambiguities are located along the line, and these are good observations that allow to achieve some centimeters accuracy.