## 3 Results and Discussion
### Post-Processing Approach
Analyzing Tables 3 and 5 (that represent the same experiments with two different antennas), it is possible to see the importance of the antenna: the geodetic one decreases the noise of results for both types of receivers and it excludes the presence of a false fix, that is present in the double constellation receiver (Table 5 (top)), even if the ambiguity fixing is not reached considering a session length of 5 min. If we compare Tables 4 and 6 it is possible to underline again the importance of the geodetic antenna, that is able to increase both the accuracy and the precision of the NVS receiver, even if the GPS constellation is considered. The next step is to analyse the performances of these two receivers in a CORSs network using the VR: we have decided to create a VR 5, 10, and 25 km from the rover to simulate the typical and maximum distance of VR positioning, respectively. Session lengths of five, ten, and 15 min were considered for these experiments. As shown in Table 7, considering a session length of five minutes, neither NVS nor u-blox receivers were able to fix the phase ambiguity; despite that, only the float solutions of u-blox receiver were quite good; considering the NVS receiver the difference between \"true\" and estimated coordinates are approximately 30 cm for each planimetric component and 50 cm for the height, while for u-blox receivers the performances obtained considering a VR five km from the rover are very good: the differences are about five cm for planimetric components and 28 cm for the height. If the distance between VR and u-blox increases, the performances were reduced and the planimetric differences were about 20 cm, even if the altimetric one was the same. The results for the differences between estimated and reference positioning are shown in Table 7. Comparing these results with Table 3, we can affirm that a session length equal to 5 min is not sufficient to fix the phase ambiguity of both receivers: despite this, no false fix can be found. It is possible to obtain decimetric accuracies even if the \(\sigma\) has values from 2 up to 5 cm. If the session length increases up to ten minutes, the performances improve and the gap between estimated and reference positions decrease; while the NVS receiver differences are greater (the only improvement is on the height), considering the u-blox receiver very good results were obtained for planimetric components. It is strange that when considering the NVS receiver and the VR five km far from the rover, the software is able to fix the phase ambiguity but provides the wrong coordinates. In \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{8}{c}{**NVS (LEIAR10 Antenna, only GPS)**} \\ \hline  & **\(\mu\)E [m]** & **\(\mu\)N [m]** & **\(\mu\)h [m]** & **\(\sigma\)E [m]** & **\(\sigma\)N [m]** & **\(\sigma\)h [m]** & \\ \hline
5 min & \(-\)0.003 & 0.018 & 0.036 & 0.005 & 0.006 & 0.009 & FIX \\
10 min & \(-\)0.001 & 0.006 & 0.019 & 0.002 & 0.003 & 0.005 & FIX \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Differences between “true” and estimated coordinates of NVS receiver using a CORS eight km from the rover with only GPS constellation and LEIAR10 antenna.