## 2 Scale Factor Calibrated Using Different AG Values
### Cross-Validation by Using Absolute Gravity (AG) Values
With further increase in the number of control stations (i.e., selecting stations Xiangcheng, Lijiang, Kunming, Panzhihua, Songpan, Ya'an, and Luzhou as the known stations), the cross-validation results (Figure 10b) show that the deviations obtained using the MBGA method decreases obviously; the average value is approximately 13 \(\upmu\)Gal, which means that the optimized AG deviations can reduce the gravity changes by approximately 20 \(\upmu\)Gal with the increasing number of known AG stations. Therefore, using the cross-validation of limited number of AG stations, reliable time-varying gravity data can be obtained by minimizing the uncertainty of the SFs and nonlinear drift. To further investigate the spatial difference of gravity values (GVs) caused by drift rate and SF, the spatial distribution of the difference of GVs obtained using the MBGA, BGA, and CLS methods in the southeastern Tibetan Plateau are visualized in Figure 11. The spatial difference of the adjustment results from the CLS and BGA methods, displayed in Figure 11a, shows that the difference caused by nonlinear drift is small, i.e., within the range of \(\pm 12\)\(\upmu\)Gal. In comparison, it is evident that the SF is the main factor affecting the gravity difference of GVs, with the maximum difference of approximately 60 \(\upmu\)Gal. The difference caused by drift rate is obvious in the larger loops or at the edge of the survey network, in which the survey time is long or where stations are not connected in a loop. The difference caused by SF is most obvious where the GD is large (e.g., in western parts of  
Figure 10: Gravity deviation of AG values obtained from actual absolute observations and from using the CLS, BGA, and MBGA methods. (**a**) taking Kunming and Ya’an AG stations into the adjustment, and (**b**) taking Xiangcheng, Lijiang, Kunming, Panzhihua, Songpan, Ya’an, and Luzhou AG stations into the adjustment. Pixian and Ya'an or to the south of Mengzi) or far from the constraint of AG stations, and this phenomenon is consistent with expectation. Finally, through adjustment of the measurement data of the six campaign periods during 2018-2020 using the CLS and MBGA methods separately, the overall data quality was evaluated comprehensively. As shown in Table 4, the accuracy of the GVs obtained using the MBGA method is better than that of the GVs derived using the CLS method, which is no more than 10 \(\upmu\)Gal, and the range of the GD residuals is 6.8-11.3 \(\upmu\)Gal. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Survey Date**} & \multirow{2}{*}{**Relative Gravieters**} & \multicolumn{2}{c}{**Accuracy of GV**} & \multicolumn{2}{c}{**SD of GV**} & \multicolumn{2}{c}{**SD of GD Residuals**} \\  & & \multicolumn{2}{c}{**(\(\upmu\)Gal)**} & \multicolumn{2}{c}{**(\(\upmu\)Gal)**} & \multicolumn{2}{c}{**(\(\upmu\)Gal)**} \\ \cline{3-8} \cline{7-9}  & & **CLS** & **MBGA** & **CLS** & **MBGA** & **CLS** & **MBGA** \\ \hline \multirow{3}{*}{March 2018} & CG-5 (\(\#\)1169, \(\#\)1170) & \multirow{3}{*}{6.8} & \multirow{3}{*}{5.9} & \multirow{3}{*}{2.2} & \multirow{3}{*}{1.3} & \multirow{3}{*}{9.3} & \multirow{3}{*}{8.2} \\  & LCR-G (\(\#\)149, \(\#\)150, \(\#\)132, \(\#\)843) & & & & & & \\ \cline{1-1} \cline{3-8}  & CG-5 (\(\#\)1169, \(\#\)1170, \(\#\)834, \(\#\)845) & & & & & & \\ \cline{1-1} \cline{3-8}  & LCR-G (\(\#\)149, \(\#\)150) & & & & & & & \\ \cline{1-1} \cline{3-8}  & LCR-G (\(\#\)149, \(\#\)150) & & & & & & & \\ \cline{1-1} \cline{3-8}  & LCR-G (\(\#\)149, \(\#\)150) & & & & & & & \\ \cline{1-1} \cline{3-8}  & CG-5 (\(\#\)1169, \(\#\)1170) & & & & & & & \\ \cline{1-1} \cline{3-8}  & LCR-G (\(\#\)149, \(\#\)150) & & & & & & & \\ \cline{1-1} \cline{3-8}  & CG-5 (\(\#\)1169, \(\#\)1170) & & & & & & & \\ \cline{1-1} \cline{3-8}  & LCR-G (\(\#\)149, \(\#\)150) & & & & & & & \\ \cline{1-1} \cline{3-8}  & GV: gravity values calculated by adjustment; SD: standard deviation; GD: gravity difference between adjacent station pairs.