## 3 Phase-Bias Results Assessment
### Comparison of the CNES Phase Biases  
The aim of this section is to compare the RT and POST code and phase Observable Specific Biases (OSB) produced by CNES with the ones computed by the School of Geodesy and Geomatics (SGG) at Wuhan University [42]. A focus is put on the stability of the difference between the CNES and the SGG biases over time. To do so, a first mean adjustment is performed. The mean value of the biases over all the satellites of a constellation and for each production center (CNES or SGG) at every epoch is subtracted from the biases. The OSB comparison is then performed with the mean-adjusted biases:  
\[\delta_{\text{OSB}}(t,s)=\Big{[}\text{OSB}_{\text{CNES}}(t,s)-\overline{\text{ OSB}}_{\text{CNES}}^{s}(t)\Big{]}-\Big{[}\text{OSB}_{\text{SGG}}(t,s)-\overline{\text{ OSB}}_{\text{SGG}}^{s}(t)\Big{]}, \tag{35}\]  
where \(\text{OSB}(t,s)\) represents any OSB product at epoch \(t\) for the satellite \(s\) and \(\overline{\text{OSB}}^{s}(t)\) is the mean over all the satellites \(s\) at epoch \(t\). Removing the mean value per constellation would have no impact from a user perspective, since this mean common term would be hidden in the clock parameter \(\tilde{h}_{t}^{s}\) defined for each constellation in Equation (23) and common to all signals emitted by the satellites of this constellation. Note that the same mean adjustment is performed for the evaluation of the Galileo High Accuracy Service (see [43,44], for instance). To evaluate the stability of the difference between the adjusted biases between both centers, the empirical standard deviation has to be computed. However, since the CNES POST and the SGG products have discontinuities at the end of each day, the standard \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**System** & **Frequency** & \multicolumn{2}{c}{**Code Bias**} & \multicolumn{2}{c}{**Phase Bias**} \\  & **RT** & **POST** & **RT** & **POST** \\ \hline \multirow{4}{*}{GPS} & L1 & C1C, C1P, C1W & C1C, C1W & L1C & L1C \\  & L2 & C2S, C2L, C2X & C2C, C2S, C2L, C2W & L2W & L2W \\  & L5 & C5Q, C5X & C5Q, C5X & L5I & L5I \\ \hline \multirow{4}{*}{GAL} & E1 & C1C & C1X & L1C & L1X \\  & E5a & C5Q & C5X & L5Q & L58X \\  & E5b & C7Q & C7X & L7Q & L7X \\  & E6 & C6C & C6X & L6C & L6X \\ \hline \multirow{4}{*}{BEI} & B1C & C1P & C1P, C1X & – & L1X \\  & B1I & C2I & C2I & L2I & L2I \\  & B2a & C5P & C5X & – & L5X \\  & B3A & C6I & C6I & L6I & L6I \\  & B2b & C7I & C7I, C7Z & L7I & L7I \\ \hline \multirow{2}{*}{GLO} & G1 & C1C & C1C & – & – \\  & G2 & C2C & C2C & – & – \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Code and phase biases computed by the PPP-WIZARD software for the DOY 2023-079 to 2023-083.  
deviation is computed over a one-day period. Then, the median of the five standard deviations for each satellite and each signal is computed and displayed in Figures 9-12. Figure 10: _Cont._  
Figure 9: Median of the standard deviations of the difference between the CNES RT /POST biases and SGG biases for the GPS constellation. Each standard deviation is computed over a period of one day. The left column depicts the RT products and the right one depicts the POST products. The first row is dedicated to the code biases and the second one to the phase biases. Figure 11: Median of the standard deviations of the difference between the CNES POST biases and SGG biases for the Galileo constellation. Each standard deviation is computed over a period of one day. The left figure depicts the code products and the right one depicts the phase products. (**a**) Code biases. (**b**) Phase biases. Figure 12: Median of the standard deviations of the difference between the CNES RT biases and SGG biases for the Glonass constellation. Each standard deviation is computed over a period of one day. Figure 10: Median of the standard deviations of the difference between the CNES RT/POST biases and SGG biases for the Beidou constellation. Each standard deviation is computed over a period of one day. The left column depicts the RT products and the right one depicts the POST products.