First geomatic restitution of the sinkhole known as "Pozzo del Merro" (Italy), with the integration and comparison of "classic" and innovative geomatic techniques

The sinkhole known as 'Pozzo del Merro' possesses unusual, geological and natural features, providing an important opportunity to study the geological and hydrological characteristics of the area, and, at the same time, to preserve an ecosystem inhabited by rare species. The site has been the object of numerous studies carried out by scholars from a wide range of disciplines, but a true morphological survey has not been performed until now due to logistical difficulties that include the lack of adequate measuring positions and the difficulty of establishing a clear view between points. The principle benefits of an accurate morphological survey include: (a) a better understanding of the geomorphological characteristics of the site, which will in turn lead to better litho-stratigraphic correlations, (b) the opportunity to obtain accurate measurements of the zero levels of several piezometric measurements, (c) the identification of any secondary cavities which might be hidden by vegetation, and (d) allowing a virtual access to the site to both researchers and general public who cannot currently visit the site due to safety issues and ecosystem vulnerability. These considerations led to the decision to undertake a detailed survey using a combination of different geomatic 'classic' techniques, including the use of total stations, GPS/GNSS geodetic surveying, and laser scanning. The availability of an imaging rover, an innovative photogrammetric multifocal instrument, suggests to repeat the survey to experiment this completely new technology.