# ADAfinder Tool Applied to EGMS Data for the Structural Health Monitoring of Urban Settlements
## 2 Materials and Methods
### Proposed Methodology  
The proposed methodology is focused on finding buildings interested by deformations above an established threshold, in urbanized areas characterized by large dataset of PSs, through ADAfinder tool. The latter is included in a procedure that, for the first time, is specific for urban districts or whole municipalities/towns. A flowchart of the proposed methodology is shown in Figure 1. The necessary data to implement the procedure are: (i) an _ESRI shapefile_ containing the polygons of the buildings plans and (ii) the two datasets referred to ASC and DES orbits, containing information about the PSs of the monitored area. Since the proposed methodology is dedicated to data processing for SHM purposes, the introduction in the flowchart of preliminary operations to be performed in a GIS software, listed in the green box of the flowchart, is needed. The preliminary operations are aimed to PSs datasets filtering to direct the procedure towards the analysis of ADAs on the buildings. First, the _ESRI shapefile_ containing polygons of the buildings plans is imported. The polygons with an area lower than 30 m\({}^{2}\) are excluded, since they are not considered to be buildings. In fact, sometimes, other little elements can be included in the available shapefiles, for example cabins, canopies, small buildings, silos, or containers in harbor areas. Then, a buffer of the polygons perimeters is done in order to take into account the inaccuracies that they might have. Since the presented methodology is focused on the buildings, all the PSs related to any other construction or reflective target have to be discarded. For this reason, a selection of the PSs intersecting the polygons (including the buffer previously mentioned) is done, while the buildings not intersected by PSs are identified and pointed out. In future, a minimum number of points, such as their distribution on the building plan, could also be added as preliminary filter of the procedure, to exclude from the analysis the buildings not well represented. Then, all the operations included in the black contour in Figure 1 are separately done using both the ASC and DES datasets. The following step is the application of the ADAfinder tool (yellow box of the flowchart). A criterion to establish the value of the stability threshold is to compare  
Figure 1: Flowchart of the proposed methodology. the V\({}_{\rm m}\) of the dataset of PSs with the relative \(\sigma\). The original source of this criterion is to assume the stability threshold at 2\(\sigma\) to exclude all the points with lower V\({}_{\rm m}\), as described in [PERSON] et al. [35]. Herein, a more conservative additional constraint is assumed, since the final goal is the identification of the critical constructions. In fact, the stability threshold is set at (i) 2\(\sigma\) if V\({}_{\rm m}<\sigma\), while it is set at (ii) 1\(\sigma\) if V\({}_{\rm m}>\sigma\). In general, if a high average value of the velocity is present (ii), it can be important to consider more constructions in the monitoring phase and then a lower threshold value can be fixed. In fact, in the case (i), the values of V\({}_{\rm m}\) are greater, and a trend of deformations more or less defined is present, so it is convenient to keep a larger number of PSs. In contrast, the case (i) usually verifies in large areas with different deformation processes included, so a great dispersion of the V\({}_{\rm m}\) values can be detected and a cut at 2\(\sigma\) is more convenient to exclude the lower deformation values. Moreover, the ADA radius (in meters) should be set, and the minimum number of PSs in an ADA has to be imposed. In the proposed methodology, it is recommended to set the minimum number of PSs equal to the minimum value accepted by the tool, that, in the current version (ADAtools 2.0.3), is 3. The operation described until this step must be carried out both for the ASC and the DES datasets.