## 4 Vertical Deflections
### Directional Components at Crossover Points
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**HY-2B Stacking Cycles**} & \multicolumn{1}{c}{**Resolution of Mean Geoid**} & \multicolumn{1}{c}{**Effect of Every Cycle Improving**} & \multicolumn{1}{c}{**Improving Percentage**} \\ \hline Reference pass & 19.98 km & — & — \\
5 cycles & 14.65 km & 1.332 km/cycle & 26.67\% \\
10 cycles & 10.94 km & 1.004 km/cycle & 45.24\% \\
15 cycles & 9.28 km & 0.713 km/cycle & 53.55\% \\
20 cycles & 7.77 km & 0.610 km/cycle & 61.11\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The average resolution capabilities and improvement effect of HY-2B stacking data. component for HY-2C and HY-2D was relatively higher and closer to the accuracy of the meridional component. As a follow-on satellite of HY-2A, HY-2B greatly enhanced the accuracy of the prime component from 5.73 to 3.67 arcsec. We attributed this improvement to better data quality due to the same inclination and higher accuracy in the meridional component. In addition, HY-2C and HY-2D showed consistent reliability with HY-2B in calculating the meridional component of vertical deflections: ~1.4 arcsec. Table 6 also shows that the statistics in Region 3 were superior to those in the other regions for all HY-2 missions. This was related to the magnitude and feature changes in vertical deflection in different areas. Hence, the distributional proportion of the directional components are calculated and plotted in Figure 8. Compared with the other regions, the meridional components of vertical deflection in Region 3 (Mid-Pacific) were relatively concentrated at 0-6 arcsec and the variation amplitude was smaller. Furthermore, the distributional proportions of the meridional component for the four HY-2 missions were consistent in each region, although the crossover point locations were different. Except for the prime components, HY-2C and HY-2D remained consistent while the distributional proportion for HY-2A and HY-2B varied, indicating gaps in the ability to determine the east-west vertical deflections. Figure 8: Distributional proportion of HY-2 directional components of vertical deflection over study regions: Region 1, North Pacific; Region 2, South Pacific; Region 3, Mid-Pacific; Region 4, Indian Ocean; Region 5, North Atlantic; Region 6, South Atlantic. Similar to Figure 8, the distributional proportions of the validation results with the XGM2019 model are plotted in Figure 9. The discrepancies between the meridional components and XGM2019 mainly fell in a range of \(\pm 1\) arcsec for all HY-2 missions. This regularity was especially prominent in Region 3 (Mid-Pacific), where the proportion of less than 1 arcsec was about 45%. The distribution was more dispersed for the prime components and a reduction of 10-20% occurred in the six study regions for the proportion of small discrepancies within \(\pm 1\) arcsec. For HY-2C and HY-2D, the proportion of less than 2 arcsec was still more than 50%. In contrast, HY-2B's ability to determine the prime components of vertical deflection was inferior to that of HY-2C and HY-2D. In addition, HY-2A had the worst performance in tracking east-west signals and abnormal results with large discrepancies were over 5%.