## 2 Materials and Methods
### Workflow
As mentioned above (see Section 2.1.3), this is the stage of the workflow when the presence of any environmental variable needs to be carefully accounted for, alongside its probable influence on the effectiveness of satellite data to make the archaeological features be well visible and detectable. If this is the case, it is always recommended that images collected in matching seasons are compared and the satellite-based surveys are repeated in different seasons. Constraints to the implementation of the above approaches may be caused by the timeline of the dam construction and its operations. If the beginning of the dam construction is imminent or the schedule of the reservoir impoundment(s) is tight, so the time allocated for archaeological surveys is short, there may not be enough opportunities to collect new images covering different seasons. Therefore, unless a sufficiently long archive of images is already available, the breadth of observations also to account for the environmental variable may be limited. On the contrary, if time pressure is absent, a combination of satellite images collected routinely according to a predefined acquisition scenario (e.g., Sentinel-2) and \"tunable data\" (e.g., COSMO-SkyMed acquisitions) can provide an adequate temporal frequency of observation. In all circumstances, the possibility to collect new satellite images suiting the purposes of rescue archaeology is recommended. While the availability of archive imagery is always a resource that should not be disregarded, it is not infrequent that these images may require a sort of repurposing to be used as they were originally collected for other scopes. The absence of archive imagery does not represent an obstacle for PCARA when dams are still to be constructed or just planned. Instead, it may be a partial to a full constraint in the case of PFRAP, meaning when the archaeological research has to be made during the construction of a dam or when the dam is already in operation. Once the baseline and satellite data have been prepared, the satellite image analyst can generate map products derived from satellite image processing that can be used by the archaeologists for manual remote sensing activities. Via geospatial analysis in a Geographic Information System (GIS) environment, the archaeologists can combine observations with information about reservoirs and associated infrastructures, and produce maps of identified sites and those at risk or that have been already damaged or lost. Although this step of the methodology mainly relies on the archaeologist's expertise, it also benefits from the multidisciplinary collaboration with the image analyst (see Section 2.1.1), in order to assess the presence of false positives, corroborate the interpretation, or iteratively go back to the satellite data selection and/or their processing to improve visibility and quality of the derived products, attempt new image elaborations or collect more data. New methods for automatic identification of sites are currently being developed and published (e.g., [70]). However, the proposed workflow intentionally focuses on manual and visual surveying for site identification, i.e., the most probable and simplest of the exploitation scenarios by field archaeologists that the present work aspires to reach and encourage towards the use of satellite data for purposes of rescue archaeology.