## 2 Test Site and Dataset
### Dataset
This was done in order to avoid acquiring images when the scenario was covered by snow. The resulting dataset at disposal represents thus a perfect test bed to demonstrate the benefits of employing the TSC approach in the PSI framework when a reduced number of SAR images is available. \begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{**RiskSAR-X**} & \multicolumn{1}{c}{**TerraSAR-X (Sliding Spotlight Mode)**} \\ \hline
**Sensor Parameter** & **Magnitude** & **Sensor Parameter** & **Magnitude** \\ \hline Carrier Frequency & 9.65 GHz & Carrier Frequency & 9.65 GHz \\ Sampling Frequency & 81 MHz & Incidence Angle & \(20\)–\(55^{\circ}\); \\ Pulse Repetition Frequency & 20 KHz & Pulse Repetition Frequency & 8.2 KHz \\ Bandwidth & 120 MHz & Bandwidth & 150 MHz \\ Deramped Signal Bandwidth & 40 MHz & Slant Range Resolution & 1.2 m \\ Transmitted Power & 27 dBm & Azimuth Resolution & 1.1 m \\
3 dB Antenna Beamwidth & 27\({}^{\circ}\) & Range Scene Size & 10 km \\ Range Time-Average Factor & \(128\) & Azimuth Scene Size & 5 km \\ Synthetic Aperture Length & 2 m & Frequency Modulation Rate & \(ca.-5700\) Hz/s \\ Scanning Time: Single-Pol / PolSAR & 1/2.5 min & Zero Doppler Scene Duration & 3.2 s \\ \hline \hline \end{tabular}
\end{table} 
Table 1: RiskSAR-X and Sliding Spotlight TerraSAR-X setting parameters. Finally, some remarks about the area of interest should be briefly commented. As seen in Figure 1a, El Forn de Canillo is mostly vegetated, containing only some bare surfaces and man-made structures suitable for PSI purposes. Figure 4 illustrates the impact of these characteristics on the amplitude of SAR acquisitions. The figure shows the amplitude of the backscattered signal covering the lower part of the landslide of El Forn de Canillo collected by the RiskSAR-X sensor, expressed in both cartesian (Figure 4a) and polar coordinates (Figure 4b), and the amplitude of the SAR images acquired with the TerraSAR-X sensor operating in spotlight mode corresponding to the whole sliding mass (Figure 4c). This figure evidences the improvement in spatial resolution achieved by the second generation SAR sensors, in particular by the X-band systems working in spotlight mode, which are making SAR images more and more geometrically comparable to optical ones, showing impressive details of the illuminated areas. A poorer spatial resolution may be appreciated for GB-SAR acquisitions mainly due to the cross-range resolution degradation in the far range. Despite this, the man-made structures, bare surfaces and rocky areas may be identified (blue arrows in Figure 4), showing high amplitude levels. Notice also how some forested areas also exhibit high values of back-scattered signal (red arrows in Figure 4). The lower values of amplitude correspond to crop fields, heavy grass areas, shrubberies, _etc_. All of the algorithms explained in this paper are addressed for the polar coordinates reference system. The fast temporal decorrelation phenomenon present at the X-band over this type of vegetated scenario represents an extra challenge to PSI techniques. The presence of large forested and vegetated areas make difficult the task of obtaining a sufficient network of high-quality phase scatterers for the later reliable displacement map retrieval. In contrast, these complex characteristics of El Forn de Canillo will allow one to easily verify the performance of the SCSs selected, which should correspond with the man-made structures, rocky areas and bare surfaces present in the illuminated area.