## 4 Discussion of the Results Analysis: First Findings on Trends and Best Practices
### Main Findings for the Scientific Literature Sample  
In the past few decades, ordinary management has become one of the fields of application where not only RS and geomatics but also non-invasive diagnostics of cultural heritage has proved to be of interest to public and private heritage-protection bodies in support of conservation procedures. In support of this finding, we identify the suggestions for an overall non-invasive approach also from the cultural heritage community itself, that  
Figure 15: Temporal distribution of hazards and damage factors, as defined according to UNESCO’s lexicon [24], in the analyzed Grey literature. Factors accounting for less than 5% each (cf. Figure 14) are all grey-colored. is to say, the requests established by Valetta convention of 1995. Over the years, there has been quite transversal evidence of such employment of such practices across Europe, from Italy to Spain and from Poland to the United Kingdom. The community of geological sciences is one of the first that historically had the need to monitor important environmental phenomena on a territorial scale and hence the access to satellite remote sensing information for civil purposes. In fact, the US Landsat program and the European Global Monitoring for Environment and Security GMES program were planned for the monitoring of environmental changes and their possible impact on society as a whole. It is in this context that several communities have historically been interested in applications to cultural heritage. This interest has translated into an increasing use of RS and EO techniques to document and monitor sudden ecological and geological events, such as earthquakes, floodings, or fires. This is easily visible in our analysis, with the corresponding UNESCO primary factor being the second most considered over the last 20 years. As a result, one of the first communities to reach maturity in the use of satellite RS for cultural heritage, to the point of publishing results and use cases with a certain temporal continuity, is the community of geological sciences focused on damage assessment, followed by the geomatics technologies sector, focused on geometric documentation and change monitoring. Evidence for this is reflected in studies reported at the European level on the use of satellite data for geohazards in cultural heritage sites [13]. Furthermore, it has been identified that, during the monitoring of hazards to cultural heritage, quite a few geomatics technologies are used simultaneously with satellite imagery, be it by remote sensing specialists, by heritage experts, or both. The suggestion for this can be found in our analysis of additional technologies used simultaneously with satellite imagery for both \"Satellite RS\" and \"Engine\" technologies (shown in Figure 10). It can be noticed that, in both cases, the geospatial framework (in terms of GIS environments for different purposes) is the predominant choice for data integration. This only indicates that the most recent trends in the EO domain link the remote sensing imagery processing even more closely with the geospatial information world, with examples that can be found in addressing user communities, such as the Copernicus user uptake within EO4 GEO [16] or more official legislative instruments such as Open Data Directive tackling public sector information (a successor to PSI Directive) [38]. Furthermore, another technological category common to both uses of satellite imagery is aerial photography, especially the branch that is increasingly relying on UAV-born imagery. This could be explained by the fact that UAV devices and the licenses needed to pilot them have had increasingly more accessible costs compared to the same technology a few years ago or, even more so compared to the photogrammetry depending on airplane flights.