## 3 Results and Discussion
### RTK Approach--Dynamic Tests  
In order to have a more complete analysis about the performances of these types of receivers and antennas, also some dynamic tests were made. All experiments were performed by mounting the antennas on a mobile vehicle, using an antenna-splitter which allowed the simultaneous GNSS reception for three receivers (the two mass-market units shown in Table 1 and the Leica Geosystems(r) Leica GX1230 geodetic receiver used only to verify the accuracy of the performed trajectories). To understand if there might be some benefits in the use of different antennas, some experiments in NRTK modality were carried out, driving complex trajectories in a parking of a shopping center, always considering the VRS stream of the Regione Piemonte CORSs network. Four different tests were performed, considering the same trajectory, shown in Figure 6:  
1. u-blox, NVS and Leica receiver with the LEIAR 10 antenna, considering GPS + GLONASS constellations
2. u-blox, NVS and Leica receiver with the LEIAR 10 antenna, considering only the GPS constellation  
Figure 5: Fixed (in green) and float (in yellow) positions obtained with NVS receiver and Garmin antenna, considering the VRS correction (RTKNAVI Window). 3. u-blox, NVS and Leica receiver with the Garmin antenna, considering GPS + GLONASS constellations
4. u-blox, NVS and Leica receiver with the Garmin antenna, considering only the GPS constellation  
In order to make the obtained results more easy to analyse, the following tables resume some statistical parameters evaluated considering the difference between the estimated (by the mass-market receivers) and the reference (by geodetic receiver) positions. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{8}{c}{**NVS (LEIAR10 Antenna, GPS + GLONASS)**} \\ \hline  & **\(\mu\)E [m]** & **\(\mu\)N [m]** & **\(\mu\)h [m]** & **\(\sigma\)E [m]** & **\(\sigma\)N [m]** & **\(\sigma\)h [m]** & **\% of Epochs** \\ \hline FIX & N/A & N/A & N/A & N/A & N/A & N/A & 0\% \\ FLOAT & \(-0.406\) & \(-0.171\) & \(0.501\) & \(0.052\) & \(0.164\) & \(0.217\) & 100\% \\ \hline \multicolumn{8}{c}{**u-blox (LEIAR10 Antenna, GPS + GLONASS)**} \\ \hline  & **\(\mu\)E [m]** & **\(\mu\)N [m]** & **\(\mu\)h [m]** & **\(\sigma\)E [m]** & **\(\sigma\)N [m]** & **\(\sigma\)h [m]** & **\% of Epochs** \\ \hline FIX & \(-0.004\) & \(-0.012\) & \(0.076\) & \(0.035\) & \(0.048\) & \(0.067\) & 85\% \\ FLOAT & \(0.131\) & \(0.530\) & \(1.088\) & \(0.023\) & \(0.109\) & \(0.240\) & 11\% \\ \hline \hline \end{tabular}
\end{table} 
Table 18: Difference between estimated and reference positioning considering the LEIAR10 antenna splitted and the GPS + GLONASS constellations. Figure 6: Trajectory performed in NRTK mode. Analysing the results with the geodetic antenna (Table 18), no epochs with fixed phase ambiguity are obtained if the NVS receiver is used. At the same time, the u-blox receiver is able to fix the phase ambiguity in 85% of epochs with a high level of precision (less than 2 cm in planimetry) and accuracy (about 5 cm in planimetry and 7 in height). Using the same antenna, the results change if the only GPS constellation is considered (Table 19): also in this case no substantial differences (in terms of precision, accuracy and percentage of epochs with fixed phase ambiguity) are obtained with the single constellation receiver while the NVS is able to fix the phase ambiguity in 72% of considered epochs, even if both precision and accuracy are less than those obtained with the u-blox.