## 3 Results and Discussion
### Post-Processing Approach
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{8}{c}{**NVS (Garmin Antenna, GPS + GLONASS, Session Length = 5 min)**} \\ \hline  & **\(\mu\)E [m]** & **\(\mu\)N [m]** & **\(\mu\)h [m]** & **\(\sigma\)E [m]** & **\(\sigma\)N [m]** & **\(\sigma\)h [m]** & \\ \hline
5 km & 0.309 & 0.294 & \(-\)0.559 & 0.038 & 0.022 & 0.046 & FLT \\
10 km & 0.303 & 0.299 & \(-\)0.525 & 0.034 & 0.026 & 0.051 & FLT \\
25 km & 0.259 & 0.279 & \(-\)0.463 & 0.036 & 0.029 & 0.050 & FLT \\ \hline \multicolumn{8}{c}{**u-blox (Garmin Antenna, only GPS, Session Length = 5 min)**} \\ \hline  & **\(\mu\)E [m]** & **\(\mu\)N [m]** & **\(\mu\)h [m]** & **\(\sigma\)E [m]** & **\(\sigma\)N [m]** & **\(\sigma\)h [m]** & \\ \hline
5 km & 0.048 & 0.018 & 0.283 & 0.012 & 0.009 & 0.034 & FLT \\
10 km & 0.162 & 0.041 & 0.264 & 0.026 & 0.018 & 0.035 & FLT \\
25 km & 0.204 & 0.018 & 0.298 & 0.030 & 0.012 & 0.033 & FLT \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Difference between estimated and reference positioning of NVS (**Top**) and u-blox **(Bottom)** receivers using a VR at various distances for a session length of five minutes. fact we have differences of about 25 and 49 cm for planimetric and altimetric components respectively, while the differences are 7 and 11 cm considering the u-blox. In this case it is possible to define the NVS position as a false fix (because the differences of \"true\" and estimated positions are greater than the L1 wavelength), which means that the software incorrectly fixes the phase ambiguity. Analysing the results obtained with a real CORS and the VR 8 and 10 km far from the rover respectively, some differences can be found. These differences were due to the feasibility of the VR: considering the NVS receiver and comparing Table 7 (top) (only for a baseline of about 10 km) with Table 3 (top) it is possible to note that better results (in terms of precision and accuracy) can be obtained with the VR. Comparing Table 8 (top) with Table 3 (top) (always for a baseline of about 10 km) the permanent station provides better results and the software for post-processing is able to fix the phase ambiguity in a correct way (Table 3 (top), 2 nd row). Considering the u-blox receiver for a session length of 5 min (Tables 3 (bottom) and 7 (bottom)) and a session length of 10 min (Tables 3 (bottom) and 8 (bottom)) and the VR 10 km far from the rover, the best results (both in terms of precision and accuracy) are obtained with the CORS. So in general it is possible to affirm that in this case this network product (VR 10 km far from the rover) is not useful for this class of receivers with this type of mass-market antenna if a real CORS is available with comparable inter-station distances. Considering the results obtained with the Garmin antenna and the VR for a session length of 5 min (Table 7) and 10 min (Table 8), no substantial differences can be found with exception of the fix of the phase ambiguity for the shortest baseline (5 km): in this case it is possible to note the false fix obtained with the double constellation receiver, as it is just seen in Table 3. If the session length increases up to 15 min, no significant improvements can be found in the results. As it is just affirmed, the software used for data post-processing is able to manage better the only GPS data (both of u-blox and NVS) than the GPS + GLONASS ones (comparison of Tables 9 and 10) probably because the GLONASS data are more noisier than the GPS ones. Focusing the attention on the type of antenna, comparing Table 9 (top) with Table 11 (top) we can affirm that the double frequency and double constellation antenna slightly improve the results considering GPS + GLONASS data while not improvement can be found if the only GPS constellation