## 4 Results Analysis
### Flight Test Case  
All the following analyses concerning the flight experiment were carried out using two receiver combinations operating in zero-baseline mode. The first combination is between JVD receivers 0081-0082, both of which are connected through external atomic clocks while the second combination is between JVD receivers 0993-0346, wherein receiver 0346 is driven through its internal TCXO. These two combinations were selected to observe any particular changes in the noise levels due to different clock configurations. Also, DD estimates from all the satellites in a constellation are superimposed in each subplot. Figure 13 depicts the L1 carrier phase DDs of the moving zero-baseline for GPS, GLONASS and Galileo with respect to GPS time. They are computed as explained in Section 3. The GNSS system specific (GPS and GLONASS) noise dispersion are almost similar for both the receiver combinations, except that the number of outliers for the first receiver combination is higher for  
Figure 12: Cumulative distribution functions (CDF) for carrier phase DDs from all satellites on L1 (**a**), L2 (**b**) and L5 (**c**) frequencies for GPS (blue), GLONASS (green) and Galileo (red). The geodetic-grade combination is displayed with solid lines, the high sensitivity combination with dashed lines. \begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**GPS L1**} & \multicolumn{3}{c}{**GLONASS L1**} & \multicolumn{3}{c}{**Gailleo L1**} \\ \cline{2-10}  & **C** & **L** & **Ratio [\%]** & **C** & **L** & **Ratio [\%]** & **C** & **L** & **Ratio [\%]** \\ \hline JVD 0081 & 39,558 & 39,558 & 0 & 37,144 & 37,144 & 0 & 28,201 & 28,201 & 0 \\ JVD 0082 & 39,795 & 39,795 & 0 & 36,647 & 36,647 & 0 & 28,177 & 28,177 & 0 \\ UBX 0867 & 46,405 & 35,368 & –24 & 45,301 & 33,940 & –25 & 33,884 & 28,034 & –17 \\ UBX 1771 & 48,402 & 36,201 & –25 & 46,028 & 33,986 & –26 & 34,475 & 28,111 & –18 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Number of L1 code range (C) and carrier phase (L) observations of three satellite systems of two geodetic-grade receivers (JVD 0081 and 0082) and two high sensitivity receivers (UBX 0867 and 1771) during the test drive. GLONASS observations compared to the second receiver combination. This is mainly due to the large number of outliers deleted for the second receiver combination during the DD estimation process compared to the first (cf. Table 4). Apart from a few outliers, the deviation of GPS L1 carrier phase is about 2 mm for the complete flight trajectory. In the case of the GLONASS L1 carrier phase, the noise is slightly higher during the start of the flight experiment (segment: start-A) compared to the other flight segments of the first receiver combination. During the segment (start-A), the aircraft was static for about 6 min and then was moving at a low velocity towards the runway. Along the complete trajectory, the sudden noisy spikes seen correspond to the flight turn, which resulted in a change of flight roll and heading angles. Overall, the deviation for GLONASS is about 5 mm for both receiver combinations, which is 2.5 times higher compared to GPS. For the first receiver combination, the spread of Galileo L1 carrier phase noise is about 2 mm for the complete flight trajectory, similar to GPS. It is also seen that the values of Galileo L1 phase noises are slightly higher at the upper altitude (segment E-G) compared to those at a lower altitude (segment A-D). Finally, there are no GNSS system specific significant changes that are seen in the computed noise levels during the highly dynamic manoeuvres (segments C-D, F-G). Similar to the urban case, the underlying process noise of the carrier phase observations are analysed with the modified ADEV's. The estimated DDs from one satellite pair of each GNSS system and two different receiver combinations are used to compute the modified ADEV's and are shown in Figure 14a. The corresponding elevation angles of the different satellites are depicted in Figure 14b.