# GNSS Positioning Using Mobile Devices with the Android Operating System
## 4 Results and Discussion
### Positioning Performances Considering Different Environments  
First, the behavior of the GNSS internal chipset was analyzed considering a post-processing approach. As it is well known, to perform a relative post-processing approach, it is necessary to consider a master station, that in this case is represented by the TORI (Turin) permanent station: this GNSS station, that belongs to the European Reference Frame (EUREF) permanent GNSS network (www.epncb.oma.be), is composed by a multi-frequency and multi-constellation receiver and a choke ring antenna and is about 250 m distance from the test sites. Both smartphones were settled in two different test sites previously cited, reference points, which coordinates were known with an accuracy level of a few millimeters. Regarding site A, the coordinate of the point was measured statically with a geodetic receiver (Leica GS14 receiver) for several hours and then post-processed. The point in site B is part of the national geodetic network. The first analyses were made considering the RTKLIB software and different positioning techniques: single point positioning (SPP), static, and kinematic. Moreover, different sessions' lengths were considered (10, 30, and 60 min) to verify if there was a correlation between the length of the session and the precision of the solutions. The results are presented in Tables 2 and 3. All solutions were obtained by applying the following atmospheric corrections. The Saastamoinen model was used to mitigate the tropospheric delay using dry and wet components, while the Klobuchar model for the ionospheric one, setting the cut off elevation as 10\({}^{\circ}\). All results were obtained fixing the phase ambiguities as integer values, according to the \"Fix and hold\" method [18]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Sites** & **Session Length** & **Method** & **East** & **North** & **Up** \\ \hline \multirow{3}{*}{A} & \multirow{3}{*}{10} & Static & 35.827 & 16.135 & 21.665 \\  & & Kin & 53.085 & 33.152 & 80.066 \\  & & SPP & 58.724 & 39.226 & 88.549 \\ \hline \multirow{3}{*}{B} & \multirow{3}{*}{10} & Static & 0.959 & 0.445 & 2.071 \\  & & Kin & 47.321 & 33.935 & 39.535 \\  & & SPP & 50.047 & 35.247 & 39.707 \\ \hline \multirow{3}{*}{A} & \multirow{3}{*}{30} & Static & 3.915 & 6.844 & 10.131 \\  & & Kin & 22.475 & 16.146 & 56.759 \\  & & SPP & 33.267 & 24.791 & 71.716 \\ \hline \multirow{3}{*}{B} & \multirow{3}{*}{30} & Static & 0.864 & 0.736 & 1.817 \\  & & Kin & 12.938 & 9.756 & 15.376 \\  & & SPP & 15.932 & 12.784 & 19.766 \\ \hline \multirow{3}{*}{A} & \multirow{3}{*}{60} & Static & 8.991 & 10.462 & 10.933 \\  & & Kin & 23.867 & 18.414 & 36.343 \\  & & SPP & 27.983 & 20.626 & 42.507 \\ \hline \multirow{3}{*}{B} & \multirow{3}{*}{60} & Static & 0.048 & 0.142 & 0.118 \\  & & Kin & 5.505 & 4.821 & 9.373 \\ \cline{1-1}  & & SPP & 6.418 & 5.791 & 11.126 \\ \hline \end{tabular}
\end{table} 
Table 2: Precision of the positioning results using Huawei P10+ in meters. Analysing the results in Tables 2 and 3, it seems that location A was noisier than B because the precision obtained in the first case was lower because of multipath effects due to reflective surfaces and limited satellites' visibility. At the same time, it seems that there was no correlation between the session length and the precision, that generally happens if geodetic or handled receivers are used. This is due to the quality of the raw measurements, that are noisier than those obtainable with other mass-market receivers, such as the u-blox. The analysis of the signal is not the topic of this paper, but the same devices were analyzed in [23]. Even in the case of the kinematic solutions, the smartphones were settled in a fixed place as a static survey. The only difference was due to the different transition matrix considered in the Kalman filter. By analyzing these results, it is possible to affirm that this kind of method was not feasible for these instruments, so it will be neglected in the following sections of this work.