Low-Cost Geomatics Surveys for Emergency Interventions on Cultural Heritage. The Case of Historic Wall in Cagliari

The documentation and metric knowledge of cultural heritage is becoming an increasingly important need, especially concerning the state of degradation of some historical assets. In this context, the metric documentation of the investigated heritage becomes fundamental for a complete knowledge of the asset to support architects and engineers in the restoration process. Recently, methods and geomatics instrumentation have been developed for the survey of cultural heritage aiming at optimizing costs and time. For example, the Apple has integrated, into its devices, a LiDAR sensor capable of providing a 3D model of spaces and objects. The paper presents the studies of their potential about the study and metric documentation of cultural heritage, in particular in cases of extreme urgency and danger of the architectural asset where the speed of survey and non-contact with it becomes relevant. We focused on the case study of a perimeter wall of a historical building. The survey was performed with two fast and expeditious geomatics methods such as the Close Range Photogrammetry (CRP) and with the LiDAR Apple sensor of the iPad Pro. The wall was also surveyed with Terrestrial Laser Scanner methodology for the validation of the results.