## 2 Data
### GPS and Leveling Datasets  
The GPS data were used for calibrating the initial InSAR result from Sentinel-1A and to assess the final InSAR result. We used data from 14 continuous GPS stations in Yunlin (Figure 2), operated by WRA and the Central Weather Bureau (CWB) [3]. As an example, Figure 3 shows the time series of coordinate changes in the East, North, and vertical directions at station LNJS in Linnei Township (see Figure 3 for the location of LNJS, and Figure 2 for Linnei). The GPS time series in Figure 3 and those for InSAR calibration in this paper were the daily coordinates computed using Bernese 5.2 based on the IGS precise GPS orbits and observed earth rotation parameters. The Bernese outputs showed that the standard errors of the daily coordinates were about 3-5 mm. The orange lines show the best fitting line for the time series and represent the displacement rates from April 2016 to April 2017. The three-dimensional rates were at the level of several mm/a, suggesting that LNJS experienced few surface displacements.  
The leveling data were used to assess the vertical velocities from Sentinel-1A. There were 406 leveling benchmarks (Figure 2) with measurements conducted in April 2016 and in April 2017, which were provided by WRA [3]. The leveling measurements were collected once a year with the precision specifications as follows. The project funder (WRA) specified the following error criteria: (1) The allowable double-run misclosure needed to be below \(2.5\sqrt{k}\) mm, where \(k\) is the distance between two neighboring benchmarks in km, and (2) the allowable loop misclosure needed to be below \(3\sqrt{k}\) mm, where \(k\) is the length of a loop. Our actual measurement results [3] showed that, in the 2017 leveling survey, the misclosures of all the 22 loops were smaller than the allowable loop misclosure (\(3\sqrt{k}\) mm), and the average standard deviation of the heights determined by precision leveling was 3.3 mm [3]. The height accuracy in the 2016 leveling survey was similar to that in 2017.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Geometry** & **Scene No.** & **Date** & **Scene No.** & **Date** \\ \hline \multirow{8}{*}{Ascending Track: 69} & 1 & 04/14/2016 & 12 & 12/22/2016 \\  & 2 & 05/08/2016 & 13 & 01/03/2017 \\  & 3 & 06/01/2016 & 14 & 01/15/2017 \\  & 4 & 07/19/2016 & 15 & 01/27/2017 \\  & 5 & 08/12/2016 & 16 & 02/08/2017 \\  & 6 & 09/05/2016 & 17 & 02/02/0217 \\  & 7 & 09/29/2016 & 18 & 03/04/2017 \\  & 8 & 10/11/2016 & 19 & 03/16/2017 \\  & 9 & 10/23/2016 & 20 & 03/28/2017 \\  & 10 & 11/04/2016 & 21 & 04/09/2017 \\  & 11 & 11/28/2016 & 22 & 04/21/2017 \\ \hline \multirow{8}{*}{Descending Track: 105} & 1 & 04/16/2016 & 8 & 12/12/2016 \\  & 2 & 06/27/2016 & 9 & 01/05/2017 \\ \cline{1-1}  & 3 & 07/21/2016 & 10 & 01/29/2017 \\ \cline{1-1}  & 4 & 08/14/2016 & 11 & 02/22/2017 \\ \cline{1-1}  & 5 & 09/07/2016 & 12 & 04/11/2017 \\ \cline{1-1}  & 6 & 10/01/2016 & 13 & 04/23/2017 \\ \cline{1-1}  & 7 & 11/18/2016 & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: The list of Sentinel-1A SAR images.  
Figure 3: Time series of GPS-derived coordinate changes in the (**a**) East–West direction, (**b**) North–South direction, and (**c**) vertical direction at the LNJS station, which is a reference station for removing displacements offset in the initial InSAR result (see Section 4.1). The fitted lines (in orange) show the change rates (\(V_{E}\), \(V_{N}\), and \(V_{h}\) ) from April 2016 to April 2017.  
Figure 2: The 14 GPS stations (red triangles), 406 leveling benchmarks (green dots), 13 rain gauge stations, and 3 groundwater wells for analysis of the InSAR result in Yunlin. Names of Yunlin’s townships are given in light gray in the background.