## 5 Discussion
### The Effect of Interference on the Selection of the Result  
This method involves using short baseline sets, where different temporal baseline thresholds can affect the results obtained. We evaluated the temporal baseline thresholds at 12, 24, 36, 48, and 60 days, leveraging the stable 12-day revisit period of Sentinel-1A. Figure 9 shows that as the temporal baseline threshold increases, subtle signals indicating small landslides gradually become more apparent. In Figure 10, two small landslides within the dotted circle were not detected using a 12-day temporal baseline threshold. However, faint signals appeared at the 24-day threshold. At 36 days, distinct signals emerged, clearly distinguishable from the non-landslide areas. These signals became more pronounced at the 48- and 60-day thresholds. The capability of this method to detect landslides relies on deformation signals within the differential interferogram. Some smaller landslides exhibit weak deformations, which are imperceptible in the 12-day differential interferogram, leading to undetected landslides. Longer time differentials showcase more evident deformation signals, enabling this method to detect smaller landslides. Interestingly, as the temporal baseline threshold increases, the signal strength of larger landslide points gradually diminishes. Hence, in selecting a temporal baseline, using a 36-day threshold for constructing short baseline sets proves effective. This threshold allows the detection of smaller landslide signals while retaining most signals from larger landslides.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Method**} & \multicolumn{3}{c}{**Total Time (Seconds)**} \\ \cline{2-3}  & **Ascending** & **Descending** \\ \hline Multi-direction & 404 & 375 \\ phase gradient stacking & 3158 & 3427 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of efficiency between the multi-direction phase gradient stacking method and the SBAS method.  
It is evident that the phase gradient stacking method is closely related to whether there are deformation signals in the temporal baseline and interferogram. According to this feature, we can select data from a fixed period of time, such as the Sentinel-1A data of 6 months or one year, and initially screen out the regions where deformations may exist over a large range. However, this approach cannot directly obtain temporal deformation information to understand the motion state. Ultimately, time series InSAR technology is needed to obtain temporal deformation of specific landslide points. This approach focuses on regions with deformation, eliminating a large number of regions without deformation, and thereby improving the efficiency with which we process and analyze data.  
Figure 10: Results of multi-direction phase gradient stacking in different temporal baseline threshold (**a**) 12 days; (**b**) 24 days; (**c**) 36 days; (**d**) 48 days; (**e**) 60 days.  
Figure 9: The results of phase gradient stacking in four directions and multi-direction phase gradient staking: (**a**) G\({}_{0}\), the result of range direction; (**b**) G\({}_{45}\), the result of a 45\({}^{\circ}\) Angle counterclockwise to the range direction; (**c**) G\({}_{90}\), azimuthal results; (**d**) G\({}_{135}\), the result of 135\({}^{\circ}\) counterclockwise and range direction; (**e**) Results of integration.