## 3 Results
### Consistency of Precise Products from Different Analysis Centers
#### 3.3.2 Glonaass  
The epoch-wise orbit and clock differences between GFZ and WHU precise products for GLONASS satellites on DOY 122 of 2020 are illustrated in Figure 4. It can be seen that the orbit and clock differences of GLONASS are larger than those of GPS, and most of the orbit and clock differences are smaller than 8 cm and 0.7 ns, respectively. The epoch-wise orbit differences of R20 satellite (marked in pink) show an anomalistic behavior, especially for the along-track and cross-track directions. The RMS values of the epoch-wise orbit differences between GFZ and WHU for R20 satellite over a day are 4.5, 11.8 and 13.1 cm in the radial, along-track and cross-track directions, respectively. For further analysis, we compute the corresponding RMS statistics of the orbit differences between ESA and GFZ, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Items**} & \multirow{2}{*}{**ACs**} & \multicolumn{3}{c}{**ACs**} \\ \cline{3-5}  & & **GFZ** & **WHU** & **CNES** \\ \hline \multirow{3}{*}{Radial (cm)} & ESA & 2.2 & 1.9 & 2.0 \\  & GFZ & – & 1.9 & 2.9 \\  & WHU & – & – & 2.5 \\ \hline \multirow{3}{*}{Along-Track (cm)} & ESA & 2.5 & 1.6 & 3.2 \\  & GFZ & – & 2.5 & 4.1 \\  & WHU & – & – & 3.4 \\ \hline \multirow{3}{*}{Cross-Track (cm)} & ESA & 2.5 & 1.6 & 2.4 \\  & GFZ & – & 2.4 & 3.5 \\  & WHU & – & – & 2.7 \\ \hline \multirow{3}{*}{Clock (ns)} & ESA & 0.08 & 0.06 & 0.08 \\  & GFZ & – & 0.13 & 0.11 \\  & WHU & – & – & 0.10 \\ \hline \multirow{3}{*}{SISRE (cm)} & ESA & 1.2 & 1.2 & 2.4 \\  & GFZ & – & 3.5 & 2.7 \\ \cline{1-1}  & WHU & – & – & 2.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: RMSs of epoch-wise differences of precise satellite orbit and clock corrections among different ACs as well as SISRE statistics for GPS satellites. Figure 3: Epoch-wise orbit and clock differences for GPS satellites between GFZ and WHU precise products on DOY 122 of 2020.  
and ESA and WI-U, which are 5.3, 9.3 and 13.1 cm, and 4.2, 6.0 and 3.9 cm in the three directions, respectively. Thus, the anomalistic behavior of the epoch-wise orbit differences of R20 satellite shown in Figure 4 may be attributed to the worse orbit determination by GFZ for this satellite on DOY 122 of 2020. Table 3 lists the corresponding statistical results of GLONASS. The radial orbit differences among different ACs fall between 2.3 and 3.5 cm for GLONASS satellites. As to the orbital differences among different ACs in the other two directions, the numerical value is at a level of approximately 4 cm, except for the cases involving CNES real-time precise products. For the inconsistency of precise satellite orbit products between CNES and other ACs, the RMS differences range from 8.9 to 9.5 cm and from 5.7 to 6.6 cm in the along-track and cross-track directions, respectively. The RMS statistics of epoch-wise differences of precise satellite clock corrections over all the available epochs and satellites between ESA and GFZ, and ESA and WHU are only 0.10 ns, while the corresponding statistics vary within a range of 0.18-0.20 ns for the other four cases. Similar to the GPS satellites, the ESA and WHU precise products achieve the best consistency for GLONASS satellites in terms of the SISRE statistics, followed by the consistency between ESA and GFZ precise products, which are 2.7 and 2.8 cm, respectively. The SISRE differences are increased to 4.9 cm between GFZ and WHU precise products, and the corresponding statistics further degrade to 5.2-5.7 cm between the CNES real-time precise products and three post-processed precise products. The SISRE inconsistency of precise satellite products among different ACs of GLONASS satellites is about twice larger than that of GPS satellites, except for the results between GFZ and WHU. For further analysis, with the use of the data over 31 days, we compute the consistency statistics of precise products between GFZ and WHU for each GLONASS satellite.