# ADAfinder Tool Applied to EGMS Data for the Structural Health Monitoring of Urban Settlements
## 3 Experimental Results
### Preliminary Operations  
The five steps of the first block of the flowchart in Figure 1 were performed for the two selected areas. The _ESRI shapefile_ containing polygons of the building plans was downloaded from _OpenStreetMap_[44].  
The distribution of the PSs in the area of the _Example_ district is shown in Figure 2a,b, for ASC and DES orbits, respectively. In Table 1, the statistics of the mean velocity V\({}_{\rm m}\) of the PSs in the selected area are reported. It can be observed that the ASC PSs are more than the DES ones (almost 50% more), and that for both the datasets, the V\({}_{\rm m}\) is lower than the \(\sigma\). The different number of PSs is probably due to the different viewing geometry of ASC and DES. The values of the V\({}_{\rm m}\) in this area are not significatively high, so the area can be considered stable. It is worth underlining, in fact, that this area was chosen for the configuration of the included constructions, and not for the entity of their deformation.  
Figure 2: Distribution of the selected PSs on the buildings of the selected area of _Example_: (**a**) ascending and (**b**) descending.  
The distributions of the PSs in the area of the _Zona Franca_ district are shown in Figure 3a,b, for ASC and DES orbits, respectively. Table 2 reports the statistics of the mean velocity \(\rm V_{m}\) of the PSs in the selected area. Also in this case, it can be observed that the ASC PSs are many more of the DES ones (about 75% more), and that for both the datasets the \(\rm V_{m}\) is lower than the \(\rm\sigma\). The values of the \(\rm V_{m}\) in this area are greater, reaching, for example, \(-10.5\) mm/y in moving away from the satellite along the ASC LoS. In particular, the greatest deformations can be observed in the southern part of the area, while the central and upper regions appear to be stable.  
The urban structure of the two case study areas is very different. As mentioned before, the _Eixample_ is characterized by the presence of adjoining buildings with small surface. In fact, about the 90% of the total number of buildings have an area lower than 1000 m\({}^{2}\). In this case, over a total of 540 buildings, 524 are covered by at least 1 ASC PS and 532 are covered by at least one DES PS. However, all the buildings, except for two, are covered by a number of PSs greater than 4. In contrast, in the area of the _Zona Franca_ district, almost half of the  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Count** & **Minimum \(\rm V_{m}\)** & **Maximum \(\rm V_{m}\)** & **Average \(\rm V_{m}\)** & \(\rm\sigma\) \\ \hline
**Ascending** & 6389 & \(-7.30\) & 6.60 & \(0.11\) & \(0.82\) \\
**Descending** & 4347 & \(-6.20\) & 7.30 & 0.15 & \(0.94\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Statistics of the mean velocity \(\rm V_{m}\) (mm/y) of the selected area of _Eixample_.  
Figure 3: Distribution of the selected PSs on the buildings of the selected area of _Zona Franca_: (**a**) ascending and (**b**) descending. (**c**) statistics of the mean velocity \(\rm V_{m}\) of the selected area.  
total number of buildings have an area greater than 1000 m\({}^{2}\). Despite the larger size, there are many buildings that do not even have one PS. In fact, over a total of 1358 buildings, only 1198 are covered by at least one ASC PS and 1111 are covered by at least one DESC PS.  
In Table 3, a summary of the number of monitorable buildings in the case study areas is reported. With respect to the total number of buildings, 4% of them are not covered by both ASC and DES PSs in _Eixample_. For _Zona Franca_, this percentage increased up to 23%. This effect could be related to the different viewing geometry of ASC and DES data and to the greater presence of reflecting elements in the area (e.g., antennas, parapets, balconies).