## 6 Conclusions  
This paper shows the application of the TSC approach to work over reduced datasets of SAR acquisitions. The performance of this novel estimator has been tested over the slow-moving landslide of El Forn de Canillo using \(10\) images collected at the X-band during a one-year measurement campaign using the UPC's LFM-CW GB-SAR sensor. To complete the study, \(10\) sliding spotlight TerraSAR-X acquisitions have been also employed for the study. The type of data and the scenario selected has provided some added value to this work. The test site, mostly vegetated and only containing a few man-made structures, has constituted an extra challenge for the technique. PSI techniques usually perform worse over areas dominated by high temporal decorrelation phenomena.  
The estimation accuracy, the number of pixel candidates and the final PSI displacement maps retrieved by means of the TSC approach proposed have been widely discussed in terms of pixel density and reliability. Furthermore, they have been compared with the so-called classical approaches, showing an improved performance on reduced datasets of SAR images. The number of pixels selected with the coherence stability and the TSC approach have been perfectly associated with the man-made structures and rocky areas present in the scenario. Both approaches have shown a similar performance in terms of PSI displacement results. Nonetheless, the resolution loss inherent to the coherence approach has led to a reduced number of pixels compared with the TSC approach (four-times less). Having higher densities in PSI results is a key factor, since it increases the precision of determining the extension of local displacements patterns and eases the characterization of the global displacement behavior. The PS approach has provided slightly higher pixel densities (roughly 10 percent more), but at the expense of including outliers in the final PSI results due to the unreliable estimation of the \(D_{A}\) index. In fact, it is a false improvement, as the low number of images makes the selection untruthful.  
RiskSAR-X and TerraSAR-X have provided consistent measurements of the landslide displacements in El Forn de Canillo, which are compatible with the available inclinometric ones. Furthermore, the observations with TerraSAR-X, with greater spatial coverage, have shown that the displacements are significantly higher in the upper part of the slope (\(\sim\)3 cm/year), defining eventually an unstable rock mass whose existence had remained unnoticed so far. Field surveys have confirmed the presence of activity indicators in this area, such as recent depressions, structural disturbance and open tension cracks.  
In conclusion, the TSC approach has been demonstrated to be an excellent choice to overcome the limitations of classical approaches, when the full-resolution of images is to be preserved and the number of SAR images available is low.  
This research work has been supported by the project TEC2011-28201-C02-01, funded by the Spanish Ministerio de Ciencia e Inovacion (MICINN), and by the Government of Andorra (Edicte de 10/04/2013, Boletin Oficial Principado de Andorra (BOPA) No. 18 de 04/17/2014). The TerraSAR-X data has been provided by the German Aerospace Center (DLR) in the scope of the project GEO0878.  
The authors would like to thank the company Euroconsult for the inclinometric results provided for the test site.