## 5 Results for AOI-1  
Over 1.49 million PSs were defined from the processing of the Sentinel-1A/B images for AOI-1 (Figure 7). The velocities along the satellite LOS at these points are classified as follows: negative values are the points moving away from the satellite (yellow to purple) typically indicating ground subsidence; positive values are the points moving towards the satellite (cyan to blue) typically indicating ground uplift; points considered as stable have velocities in the range of \(\pm\)1.5 mm/year (in green), which corresponds to the accuracy obtained by past ground validation of C-band satellites such as ERS-1/2 and ENVISAT [58].  
The distribution of PSs strongly depends on the reflectivity and coherence characteristics of objects on the ground. The highest point densities are obtained in the Burren area (density of 3407 points/km\({}^{2}\)), where limestones outcrop with very limited or totally absent vegetation cover. High point densities were also obtained in Galway city (density of 2545 points/km\({}^{2}\)) and in the towns of Oranmore, Tuam, Athenry, and Gort. Although the average point density obtained over the vegetated lowlands (density of 302 points/km\({}^{2}\)) is more than ten times lower, and in many parts points are lacking entirely, the regional road network in these areas can be recognized, probably as consequence of back-scattering from buildings along these roads. The monitored territory appears to be generally stable. No large-scale areas (>10 km\({}^{2}\)) of movement have been detected.  
In contrast, only 499,478 PSs are obtained from applying the same processing to the ENVISAT dataset (Figure 8)--about one third of the number obtained from the Sentinel-1 imagery. Most of the points are again located in the outcrop-dominated areas of the Burren, but the density here is 1331 points/km\({}^{2}\). Although also sparser, the PSs distribution again defines well the urban areas of Galway city, Tuam and Atherny. The rural road networks are not visible in the ENVISAT results, however, as consequence of the far lower PSs density of only 57 points/km\({}^{2}\) obtained for the lowlands.  
In detail, the velocity map derived from Sentinel-1 imagery (Figure 7), however, shows several small-scale (<1 to 6 km\({}^{2}\)) areas of movement. We categorize these into instabilities affecting anthropic or natural environments. The first category generally comprises local subsidence affecting areas of recent urban development, the road/railway network and the embankments along the coastal areas. The second can be recognized as landslides or unstable slopes occurring along the coastline and as subsidence or uplift (or both) occurring in peatlands. There is no direct evidence of ground  
Figure 7: LOS velocity map of AOI-1 obtained from Sentinel-1A/B images with the PS-InSAR approach. SAR imagery date range: May 2015–March 2018. The sketch illustrates the satellite’s acquisition direction in respect to the orbit (**right**) and the LOS angle in respect to the vertical direction (**left**). The white pins mark the location of the selected areas described in detail in the manuscript. The red box is the area selected to extract the PSs for the statistical analysis. Base image source: Esri, DigitalGlobe, GeoEye, Earth Geographics, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community.  
movements related to the development of karst features, even if some of the detected instabilities could be explained by active karst processes.