## 4 Discussion of the Results Analysis: First Findings on Trends and Best Practices
### Main Findings for the Scientific Literature Sample
Similar consideration can be made for UAV-photogrammetry as well: because commercial software, with robust algorithms for stereo-models and orthophoto production, have stable costs and ever-improving user-friendly interfaces, UAV photogrammetry is increasingly being used by non-geomatics experts. The \"Ground sensors\" category seems to be making a more substantial difference when used simultaneously with remote sensing imagery: while this kind of sensor is used only in two cases employing the \"Engine\" modality, it amounts to almost 10% of use with the \"Satellite RS\" modality. Such behavior indicates that \"Ground sensors\" are still more employed when the processing of satellite imagery is required, often to complement such statistical analysis or to serve as a ground truth for the calibration of satellite imagery [39; 40]. Additionally, the cost of employment of ground sensors such as spectrometers or Ground Penetration Radar (GPR), together with RS expertise, often requires larger collaboration frameworks, e.g., specific dedicated projects [41; 42; 43; 44]. The growing interest of the scientific community in using satellite imagery to study the \"Other human activities\" factor (e.g., conflict or looting) can be explained in relation to the media attention that recent events such as wars and collateral damage have received in multiple countries worldwide [45; 46]. The reason for this can be found in the fact that, for specific events such as armed conflicts, the employment of remotely acquired high- and medium-resolution satellite imagery was often the only way of establishing that the damage has occurred and, hence, the only way of evaluating its extent. As a result, this has probably encouraged the scientific community to deal with other types of \"human activities\" also occurring in times of non-crisis (e.g., looting). However, this does not necessarily constitute a temporal association between events and studies, as observed in recent studies [4]. As already mentioned, what remains surprising is the almost absent analysis of the impact of large-scale damage to, for example, buildings and development, transportation infrastructure, and biological resource use/modification (e.g., agriculture). Indeed, these factors represent a daily threat to cultural heritage if not adequately regulated. This is confirmed by the growing number of reports issued by national and international institutions and NGOs, including UNESCO, ICCROM, and ICOMOS. Furthermore, they can be easily documented and monitored thanks to RS and EO technologies [47; 48; 49]. With reference to the geographical distribution of affiliations, it is not surprising that the four (4) most represented countries (Italy, UK, Cyprus, and Germany) are also among the European countries that exhibit most of the following characteristics: (i) long heritage-conservation history (e.g., dedicated regulations and public facilities responsible for conservation); (ii) research centers, institutes, universities, and a national scientific community with well-known heritage-related expertise (which are also able to attract researchers of different nationalities and develop new technological solutions); and (iii) high exposure to different risk factors given the geo-topographic and territorial conformation (e.g., a number of case studies of Italy and Cyprus).