## 4 Results and Discussion
### Satellite Laser Ranging Validation  
Limited to the CHAMP and GRACE-A missions, which are equipped with an LRR, Table 4 summarizes the laser ranging residuals statistics for the two missions using normal point data available from (1) all stations and (2) a high-quality subset of 12 stations. The station selection was applied in \begin{table}
\begin{tabular}{l l l l l l l l l l l} \hline \hline  & \multicolumn{3}{c}{**Position (cm)**} & \multicolumn{3}{c}{**Velocity (mm/s)**} \\ \cline{2-10}
**ID** & **Radial** & **Along** & **Cross** & **3D** & **Radial** & **Along** & **Cross** & **3D** \\ \hline \multicolumn{10}{l}{**CHAMP:**} & vs. WEGC-BC \\ \hline WEGC-BI & \(0.40\pm 0.09\) & \(0.82\pm 0.23\) & \(0.74\pm 0.31\) & \(1.20\pm 0.31\) & \(0.005\pm 0.001\) & \(0.005\pm 0.001\) & \(0.006\pm 0.002\) & \(0.010\pm 0.002\) \\ WEGC-NC & \(2.11\pm 0.51\) & \(3.16\pm 1.77\) & \(1.35\pm 0.39\) & \(4.10\pm 1.75\) & \(0.023\pm 0.012\) & \(0.023\pm 0.007\) & \(0.028\pm 0.015\) & \(0.044\pm 0.019\) \\ UCAR & \(1.67\pm 0.75\) & \(2.47\pm 2.20\) & \(1.24\pm 0.48\) & \(3.31\pm 2.26\) & \(0.015\pm 0.011\) & \(0.015\pm 0.011\) & \(0.018\pm 0.016\) & \(0.028\pm 0.022\) \\ EUM & \(1.96\pm 0.55\) & \(28.12\pm 2.04\) & \(1.45\pm 0.40\) & \(3.78\pm 2.05\) & \(0.025\pm 0.014\) & \(0.024\pm 0.005\) & \(0.029\pm 0.014\) & \(0.046\pm 0.020\) \\ AIUB & \(0.89\pm 0.10\) & \(1.19\pm 0.36\) & \(0.90\pm 0.26\) & \(1.76\pm 0.37\) & \(0.018\pm 0.001\) & \(0.017\pm 0.001\) & \(0.024\pm 0.001\) & \(0.034\pm 0.002\) \\ \hline \multicolumn{10}{l}{**GRACE-A:**} & vs. WEGC-BC \\ \hline WEGC-BI & \(0.39\pm 0.07\) & \(0.78\pm 0.32\) & \(0.68\pm 0.22\) & \(1.13\pm 0.33\) & \(0.005\pm 0.001\) & \(0.005\pm 0.002\) & \(0.006\pm 0.002\) & \(0.009\pm 0.003\) \\ WEGC-NC & \(0.76\pm 0.12\) & \(4.01\pm 0.12\) & \(0.85\pm 0.25\) & \(4.17\pm 0.15\) & \(0.025\pm 0.001\) & \(0.026\pm 0.001\) & \(0.035\pm 0.002\) & \(0.050\pm 0.002\) \\ UCAR & \(3.04\pm 0.36\) & \(3.29\pm 0.52\) & \(1.84\pm 0.35\) & \(4.86\pm 0.58\) & \(0.038\pm 0.002\) & \(0.038\pm 0.002\) & \(0.045\pm 0.002\) & \(0.070\pm 0.003\) \\ AIUB & \(0.60\pm 0.08\) & \(4.03\pm 0.13\) & \(1.16\pm 0.33\) & \(4.25\pm 0.16\) & \(0.021\pm 0.001\) & \(0.022\pm 0.001\) & \(0.033\pm 0.001\) & \(0.045\pm 0.001\) \\ \hline \multicolumn{10}{l}{**Metop-A:**} & vs. WEGC-BC \\ \hline WEGC-BI & \(0.48\pm 0.07\) & \(0.97\pm 0.13\) & \(0.71\pm 0.18\) & \(1.31\pm 0.16\) & \(0.006\pm 0.001\) & \(0.006\pm 0.001\) & \(0.007\pm 0.001\) & \(0.011\pm 0.001\) \\ WEGC-NC & \(3.04\pm 0.22\) & \(2.09\pm 0.33\) & \(1.56\pm 0.31\) & \(4.02\pm 0.32\) & \(0.028\pm 0.005\) & \(0.026\pm 0.005\) & \(0.025\pm 0.007\) & \(0.046\pm 0.009\) \\ UCAR & \(2.76\pm 0.45\) & \(2.99\pm 0.57\) & \(2.66\pm 0.45\) & \(4.90\pm 0.61\) & \(0.029\pm 0.003\) & \(0.029\pm 0.003\) & \(0.032\pm 0.003\) & \(0.052\pm 0.004\) \\ EUM & \(2.88\pm 0.16\) & \(2.58\pm 0.24\) & \(2.41\pm 0.65\) & \(4.59\pm 0.44\) & \(0.023\pm 0.003\) & \(0.025\pm 0.003\) & \(0.029\pm 0.005\) & \(0.045\pm 0.006\) \\ \hline \multicolumn{10}{l}{**Metop-B:**} & vs. WEGC-BC \\ \hline WEGC-BI & \(0.49\pm 0.08\) & \(0.99\pm 0.15\) & \(0.72\pm 0.20\) & \(1.33\pm 0.20\) & \(0.006\pm 0.001\) & \(0.006\pm 0.001\) & \(0.007\pm 0.001\) & \(0.011\pm 0.001\) \\ WEGC-NC & \(3.14\pm 0.28\) & \(2.38\pm 0.36\) & \(1.43\pm 0.32\) & \(4.21\pm 0.39\) & \(0.028\pm 0.005\) & \(0.026\pm 0.004\) & \(0.029\pm 0.007\) & \(0.048\pm 0.008\) \\ UCAR & \(3.08\pm 0.47\) & \(3.02\pm 0.53\) & \(3.04\pm 0.48\) & \(5.31\pm 0.61\) & \(0.032\pm 0.004\) & \(0.030\pm 0.004\) & \(0.035\pm 0.004\) & \(0.056\pm 0.005\) \\ EUM & \(3.08\pm 0.17\) & \(2.95\pm 0.33\) & \(1.92\pm 0.44\) & \(4.70\pm 0.34\) & \(0.024\pm 0.003\) & \(0.026\pm 0.003\) & \(0.032\pm 0.005\) & \(0.048\pm 0.006\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Orbit comparison for position and velocity in radial, along-track, cross-track, and corresponding 3D-RMS for different orbit solutions compared to WEGorder to discriminate between different performance levels among the stations of the ILRS network [44].