# A New Online Service for the Validation of Multi-GNSS Orbits Using SLR
## 3 Results
### Assessment of the Orbit Quality  
Orbit quality assessment based on the results coming from the SLR validation is the most obvious and popular application of the SLR observations to the GNSS constellation. The results of such kind of analyses are systematically published in reference to the different orbit models [1; 24; 25; 26; 27; 28; 49; 50; 51; 52; 53; 54; 55; 56; 57]. The major innovation introduced by the GOVUS system is the near-real time of calculations and a remarkable ease of repeatability of performed analyses for every user. Consequently, the user can perform analyses on the daily updated dataset, without any processing efforts. The latest, complex SLR validation results were published in [1] for the period 1 January-30 June 2016. In June 2017, the ILRS instructed all ACs to change the reference frame of the laser station coordinates in their processing routines from the SLRF2008 to the new release of SLRF2014. We reprocessed all the results using a new processing routine with SLRF2014. Therefore, we can compare the SLR validation results delivered by [1] and GOVUS in the corresponding period and evaluate the impact of the change. Table 2 provides a comparison between the mean offsets and standard deviations provided in [1] and delivered by GOVUS. Initially, we exclude gross outliers, which exceed 1000 mm for BeiDou IGSO and QZSS, 500 mm for BeiDou MEO and 250 mm for other types of satellites. The results delivered by MGEX and GOVUS are comparative. The main difference is visible for GLONASS satellites. The core statistics for MGEX and GOVUS equal \(5\pm 50\) and \(-12\pm 36\) mm, respectively. After the change of the reference frame, the standard deviation of validation results improved for each satellite system: 50 to 36, 45 to 38, 43 to 34, 65 to 52, 145 to 132 and 260 to 248 mm, for GLONASS, Galileo IOV, FOC, BeiDou MEO, IGSO and QZSS, respectively. Table 3 provides validation results for the extended period 1 January 2016-31 July 2017, taking into account various sets of SLR stations: (1) stations equipped with different detectors [58] (CSPAD, MCP, and PMT); (2) TOP10 stations; and (3) all available stations. Initially, we exclude gross outliers, which exceed 500 mm for all SLR residuals. As TOP10 we chose stations, which deliver more than 1000 normal points of stable observations, i.e., with no discontinuities in the time series in the analyzed period and did not indicate any dependencies between SLR residuals and the observational frame with respect to the azimuth and elevation angle. The list of TOP10 stations includes: Graz 7839, Herstmonceux 7840, Mount Stromlo 7825, Wettzell 7827 and 8834, Yarragadee 7090, Matera 7941, Greenbelt 7105, Brasilia 7407 and Potsdam 7841. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Source**} & \multicolumn{2}{c}{**GLONASS**} & \multicolumn{4}{c}{**Galileo**} & \multicolumn{4}{c}{**BeiDou**} & \multicolumn{4}{c}{**QZSS**} \\ \cline{2-13}  & \multicolumn{2}{c}{**ALL**} & \multicolumn{2}{c}{**IOV**} & \multicolumn{2}{c}{**FOC**} & \multicolumn{2}{c}{**MEO**} & \multicolumn{2}{c}{**IGSO**} & \multicolumn{2}{c}{**ALL**} \\ \cline{2-13}  & **AVG** & **STD** & **AVG** & **STD** & **AVG** & **STD** & **AVG** & **STD** & **AVG** & **STD** & **AVG** & **STD** \\ \hline COM (MGEX) \({}^{*}\) & \(5\) & \(50\) & \(-43\) & \(45\) & \(-35\) & \(43\) & \(-34\) & \(65\) & \(-28\) & \(145\) & \(-20\) & \(260\) \\ COM (GOVUS) \({}^{**}\) & \(-12\) & \(36\) & \(-45\) & \(38\) & \(-31\) & \(34\) & \(-12\) & \(52\) & \(-19\) & \(132\) & \(-18\) & \(248\) \\ \hline \hline \end{tabular}  
* results from MGEX (SLRF2008); ** results from GOVUS (SLRF2014).  
\end{table} 
Table 2: SLR residual offsets (AVG) and standard deviations (STD) for the period 1 January–30 June 2016. Values in mm. Table 3 indicates the heterogeneity of SLR measurements to the multi-GNSS satellites, i.e., the dependency on the chosen dataset of laser stations.