## 3 Dataset and Methodology
### Sentinel-1 DInSAR Applied to Dry Andes
Therefore, the range of detectable displacement, from 2.2 cm/year to 170 cm/year, almost covers the entire displacement values recorded in the literature for the observed phenomena [5; 10; 19]. In particular, rock glaciers do not exceed point displacements of more than 300-400 cm/year [22]. Maximum values are typically lower than 100 cm/year. The dataset used consisted of all possible interferometric pairs covering the selected area with temporal baselines of less than 48 days. The acquisition period ranges from October 2014 to April 2017, containing up to two hundred available images distributed in four orbital trajectories, two ascending and two descending. The images used were acquired in Interferometric Wide swath (IW) mode with polarity VV. The final set of selected interferograms consisted of eleven interferograms in the austral summer of 2014 and 2016 (December/March), three in the autumn/winter of 2015 (April/July), and two in the autumn of 2017 (April), as shown in Table 2. Each interferogram consisted of two entire Sentinel-1 frames. The off-nadir angles covered the entire spectrum available for the standard IW mode of this sensor, between 33\({}^{\circ}\) and 48\({}^{\circ}\)[65]. The interferograms were generated and unwrapped using the software developed by the Geomatics Division of the CTTC (Technological Center and Telecommunications of Catalonia) [66]. The 1 arc-second (about 30-m) resolution SRTM (Shuttle Radar Topography Mission) [67] was used to remove the topographic contribution to the phase of the interferograms. The final interferograms were generated using a multilook of five pixels in range to reduce the level of noise. The large number of processed images enabled researchers to choose interferometric pairs of high quality in terms of coherence or noise. The atmospheric component is not a critical issue in this work, since the maximum dimensions of the objects observed (less than 2 km\({}^{2}\)) are small enough to have a significant contribution from the atmospheric phase component. Moreover, since the focus is not on the magnitude of the deformations, the moderate presence of any source of systematic errors, such as atmosphere, does not affect the interpretation of the results. The final resolution of the interferograms is approximately 15 m and the minimum area of motion detection was defined in 2 ha. The inaccuracy of the Digital Elevation Model (DEM) used to determine the topographic component is another possible source of error (\(\sigma_{\text{DEM}}\)). The effects of \(\sigma_{\text{DEM}}\) in the interferometric phase are proportional to the distance between the satellite position at different acquisition times [63]. However, as commented on above in this document, the Sentinel-1 constellation orbits are in a 300 hundred m-diameter tube, which assures a low sensitivity to DEM errors. In particular, for our dataset, the worst perpendicular baseline is 65 m, which in the case of low noise, means a maximum probable DEM error of 15 m. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Temporal Baseline [Days]** & \
\begin{tabular}{c} **Minimum Detectable** \\ **Displacement [cm/Year]** \\ \end{tabular} &
\begin{tabular}{c} **Maximum Detectable** \\ **Displacement [cm/Year]** \\ \end{tabular} \\ \hline
6 & 17 & 170 \\
12 & 8.5 & 85.2 \\
24 & 4.2 & 42.6 \\
36 & 2.9 & 28.4 \\
48 & 2.2 & 21.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Rough estimation of the minimum displacement rate in an interferogram as a function of the temporal baseline for the C-Band of Sentinel 1.