## 5 Discussion
### Limitations  
The interferograms provided by LiCSAR are multilooked to \(\sim\)100 m resolution and strongly spatially filtered for the main purpose of the LiCS project (i.e., large-scale deformation monitoring and tectonic strain mapping), as mentioned in Section 2.1. Although km-scale deformations can be accurately detected, as demonstrated in Section 4, the LiCSAR products are not optimized for more localized deformation studies such as infrastructure monitoring.  
LiCSBAS deals with gaps in the SB network by imposing a temporal constraint at the inversion step (Step 1-3; Section 2.4.3). We note that the interpolated displacement between the gaps might not be realistic if the true deformation is not linear. It is difficult to quantify the uncertainty of the derived  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Entire Frame** & **Echigo Plain** &
\begin{tabular}{c} **Entire Frame (10 \(\times\) 10** \\ **Downsampled)** \\ \end{tabular} \\ \hline Size of Image & 3338 \(\times\) 2685 & 732 \(\times\) 922 & 333 \(\times\) 268 \\ \# of Images & 104 & 104 & 104 \\ \# of Interferograms & 306 & 306 & 306 \\ \# of Inverted Pixels (at & & & \\ Step 1-3) & 2,503,334 & 288,079 & 24,579 \\ \# of Remaining Pixels & & & \\ (after Step 1-6) & 1,166,756 & 167,269 & 15,704 \\ \hline Step 0-1 & 10 min & — & — \\ Step 0-2 & 10 min & — & 3 min \\ Step 0-3 & 30 min & — & 5 min \\ Step 0-4 & 5 min & 2 min & 1 min \\ Step 0-5 & — & 5 min & — \\ \hline Step 1-1 & 2 min & \(<\)1 min & \(<\)1 min \\ Step 1-2 & 20 min & 4 min & 3 min \\ Step 1-3 & 3 hr 30 min & 25 min & 5 min \\ Step 1-4 & 20 min & 2 min & \(<\)1 min \\ Step 1-5 & \(<\)1 min & \(<\)1 min & \(<\)1 min \\ Step 1-6 & 30 min & 5 min & 2 min \\ \hline Total Time for Step 1 & \(\sim\)5 hr & \(\sim\)40 min & \(\sim\)10 min \\ \hline Size of Downloaded & & & \\ GeoTIFF & 5 GB & — & — \\ Size of GACOS Data & 5 GB & — & — \\ Size of Converted Data & 21 GB & 2 GB & 0.2 GB \\ Size of Created Data in & 10 GB & 1 GB & 0.2 GB \\ Step 1 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Processing time and disk usage of LiCSBAS in the case studies.  
time series with gap, and the potential bias should be carefully considered. Gaps are easily identified in the time series viewer to aid in interpretation.  
Densely vegetated areas, including large portions of Japan, suffer from incoherence in C-band data, even with the short temporal baselines of Sentinel-1, compared to earlier radar satellites (see Section 3). In this study, the minimum acquisition interval is 12 days versus 6 days for Sentinel-1 across Europe [12]. Quite a few of the 12-day interferograms retain sufficient coherence over the frame, whereas most of the 24-day and longer interferograms lose coherence in the vegetated areas (Figure S13). In general, the coherence decays exponentially with time [70; 71]. More frequent acquisition intervals (i.e., 6 days) increase the likelihood of retaining coherence at C-band and detecting deformation over vegetated areas [72].  
Another possible solution for the vegetated areas is exploitation of L-band data. Although abundant L-band data like Sentinel-1 are currently not available, several new planned L-band satellites missions, such as ALOS-4 and NISAR, are capable of frequent, wide-swath observations. LiCSBAS can also be used to process data from other satellites (see Section 2.2).