3-D Survey of Rocky Structures: The Dolomitic Spire of the Gusela del Vescovà

Abstract

In the mountain environment, the presence of fractures or degradation in the rock mass could represent an important risk both for the safety of population and for the anthropic structures that have a productive, touristic and/or historical importance. For this reason, the monitoring is a primary action of control and risk mitigation. In this work a 3-D survey of the Gusela del Vescova’ Dolomitic Spire was performed for the morphometric definition of its rocky elements using Terrestrial Laser Scanning (TLS) and Structure from Motion (SfM) applied to drone-captured imagery; the georeferencing was executed using classical topographic and GNSS methodologies. Results provides information about the state of the structure after 18 years from the first measurement (2001–2019) of the main fracture and models obtained with the two methodologies, allowing the evaluation of advantages and disadvantages of the techniques for the survey in extreme environment conditions. The comparison between the models, together with GCP’s errors estimate, allowed to evaluate the final 3-D models: in this case SfM model shows a better global quality in terms of completeness and photo-realistic representation, with high accuracy that is comparable to the TLS models. This survey provides the first complete 3D high resolution representation of the spire: an up-to-date geometrical and photographic dataset that allows accurate measures, the definition of the cracks pattern and represents the base for further future studies and monitoring of the deformations.