## 4 Results Analysis  
### Urban Test Case  
The measurement configuration offers the possibility to compare the signal quality of geodetic-grade and high sensitivity equipment. Therefore, two combinations (JVD 0081-JVD 0082 and UBX 0867-UBX 1771) are utilised to compute DD based on the strategy developed in Section 3. These two configurations are selected to point out major differences in the noise levels of the observed carrier phases for different GNSS systems. Note that the corrected DDs of all satellites are superimposed per system in each figure. Since the UBX receivers are only capable of tracking one frequency per system, the C/A code based carrier phase observations on the L1 frequency are analysed. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Rec. pair**} & \multicolumn{2}{c}{**\# Observations**} & \multicolumn{3}{c}{**\# Cycle Slips**} & \multicolumn{3}{c}{**\# Outliers**} & \multicolumn{3}{c}{**\# Ambiguities**} \\  & **GPS** & **GLO** & **GAL** & **GPS** & **GLO** & **GAL** & **GPS** & **GLO** & **GAL** & **GPS** & **GLO** & **GAL** \\ \hline JVD (urban) & \multirow{2}{*}{38,157} & \multirow{2}{*}{35,387} & \multirow{2}{*}{27,517} & \multirow{2}{*}{1632} & \multirow{2}{*}{1154} & \multirow{2}{*}{569} & \multirow{2}{*}{851} & \multirow{2}{*}{794} & \multirow{2}{*}{189} & \multirow{2}{*}{3318} & \multirow{2}{*}{3028} & \multirow{2}{*}{582} \\  & 081-0082 & & & & & & & & & & & \\ \hline UBX (urban) & \multirow{2}{*}{34,805} & \multirow{2}{*}{33,399} & \multirow{2}{*}{27,783} & \multirow{2}{*}{723} & \multirow{2}{*}{1064} & \multirow{2}{*}{80} & \multirow{2}{*}{407} & \multirow{2}{*}{632} & \multirow{2}{*}{116} & \multirow{2}{*}{3082} & \multirow{2}{*}{3249} & \multirow{2}{*}{1160} \\  & 0867-1771 & & & & & & & & & & & \\ \hline JVD (aerial) & \multirow{2}{*}{136,285} & \multirow{2}{*}{87,464} & \multirow{2}{*}{75,594} & \multirow{2}{*}{82} & \multirow{2}{*}{68} & \multirow{2}{*}{40} & \multirow{2}{*}{59} & \multirow{2}{*}{71} & \multirow{2}{*}{43} & \multirow{2}{*}{426} & \multirow{2}{*}{419} & \multirow{2}{*}{174} \\  & 081-0082 & & & & & & & & & & & \\ \hline JVD (aerial) & \multirow{2}{*}{136,167} & \multirow{2}{*}{87,660} & \multirow{2}{*}{-} & \multirow{2}{*}{342} & \multirow{2}{*}{193} & \multirow{2}{*}{-} & \multirow{2}{*}{180} & \multirow{2}{*}{192} & \multirow{2}{*}{-} & \multirow{2}{*}{750} & \multirow{2}{*}{676} & \multirow{2}{*}{-} \\  & 0993-0346 & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: GNSS L1 DD computation statistics for different receiver combinations from both experiments. Figure 8 shows the L1 carrier phase noise of GPS, GLONASS and Galileo with respect to GPS time. The DDs of the geodetic-grade combination are depicted in the upper row while the DDs of the high sensitivity combination are depicted in the lower row. The DD noise of the different systems does not differ very much and vary roughly between \(\pm\) 2 mm (Figure 8a,c). However, there are many outliers of up to 15 mm, which affects the time series. The same applies to the DDs of the UBX receivers. The major difference is the general magnitude of noise, which is more than doubled to roughly \(\pm\) 5 mm. The data gap in the GLONASS time series in Figure 8b results from the single difference bias computation (cf. Section 3). The integer DD ambiguity can be estimated if the bias term is smaller than 0.1 cycles. In order to keep the bias term smaller than 0.1 cycles, the single difference ambiguity must be known with an accuracy of 285 cycles for the minimum wavelength difference between two satellites. Similarly, this ambiguity must be known with an accuracy of 12 cycles for the maximum wavelength difference between two satellites [37]. This requirement for determining the single difference bias term is not met at these epochs and hence, a further analysis of the DD is not feasible. This is the reason why they are simply deleted.