UAS AERIAL DIGITAL PHOTOGRAMMETRY FOR LANDSCAPE MODELING AND REHABILITATION DESIGN OF THE "SAN FRANCESCO" ABANDONED MINE (SARDINIA-ITALY)

In the Ottana-Orani mining district (Central Sardinia - Italy) several talc-chlorite bodies, hosted in Palaeozoic metamorphics rocks and granites, have long been exploited. Most of these operations are underground excavations but mining activity have deeply modified natural landforms with a lot of landfills and trenches in the "San Francesco" area where a rehabilitation project should be considered as an overall project of landscape restoration. In this research field the aerial digital photogrammetry is an important tool for the realization of detailed 3D digital surface model (DSM) required for any realistic visualization during the development of a restoration planning. In this work we report the results of a proximal photogrammetric survey using an unmanned aerial system (UAS) and based on the acquisition of non-metric high resolution digital images, to generate detailed 3D models. This method is especially designed for sites with a complex topography and high morphological steepness (vertical walls, deep excavation holes, slopes) and allows to create digital terrain models (DTM) at different consistent resolution (where different survey altitude is required). The survey was based on geo-referenced GPS grid and the aerial images dataset was processed with different hotogrammetric software to obtain geo-referenced orthomosaic, DSM, DTM and 3D models. Finally we have carried out a realistic 3D digital reconstruction and rendering, that constitute a powerful and sophisticated method to manage landscape design into restoration projects.