3D METRIC DOCUMENTATION USING GEOMATIC METHODS. Integrated and multi-sensor 3D metric survey

The digitization projects of architectural heritage are a field of research continuously evolving and updating in parallel to technological innovations that allow to progressively boosting the challenges and requirements of the geometric and semantic richness of related digital models. Today, the XX century heritage typically necessitates urgent and attentive conservation plans that require multidisciplinary research and profound investigation of new and tailored approaches providing a clear indication of best practices and recommendations for correct 3D documentation, and for information management by suitable digital systems. The multi-sensor approach is organized by combining different range and image-based techniques in order to generate a multi-scale 3D model. The use of UAV (Uncrewed Aerial Vehicle) photogrammetric approach was conceived for the documentation of the articulated complex in the outdoor spaces (concerning extrados surface). In the indoor environments, the hierarchy of documentation requires the use of different techniques: static LiDAR used for the main halls structural elements, was flanked by Mobile Mapping System (MMS) by SLAM-based portable technologies in case of non-straightforward accessibility of enclosed spaces, galleries, and underground rooms. The first paragraph extensively describes the methods adopted, the specific characteristics of their application according to the diverse needs that the articulated spaces of the Turin Exhibition Center required.