ViDoc RTK Device for Ancient Walls Surveying: Accuracy Assessment and Validation with Geomatic Techniques

The documentation and monitoring of ancient masonry structures require high-precision surveying techniques to assess their geometry and structural evolution over time. This study introduces the viDoc RTK rover integrated with a smartphone as an innovative approach for heritage documentation, applied to the cyclopean walls of Amelia, a historic town in Umbria (Central Italy). The walls have long been subject to a geomatic monitoring system following a collapse, and periodic surveys – including GNSS, robotic total station, photogrammetric survey, and laser scanning – have been conducted to evaluate their structural integrity and ensure their preservation. The viDoc RTK system was used to generate a high-resolution 3D model of the walls, offering a level of detail comparable to Terrestrial Laser Scanning (TLS), but with greater flexibility and efficiency in terms of costs and weight. To validate the accuracy of the viDoc device, high-precision total station measurements were performed on materialized points on the walls – mini-prisms belonging to a monitoring network surveyed periodically with a robotic total station – while a TLS survey provided a dense point cloud of the entire wall surface. The accuracy of the viDoc system was assessed through two complementary approaches. A discrete comparison was performed on the materialized points on the walls, where mini prisms were placed and measured with millimeter accuracy by means of a high accuracy robotic total station. Additionally, a quasi-continuous comparison was conducted using the laser scanning point cloud, which, despite its lower accuracy (centimeter level), provides a detailed 3D representation of the wall surface. The results show the potential of the viDoc system as a fast, efficient, and detailed solution for the 3D documentation of historic masonry structures. Compared to traditional techniques, it offers a more accessible and versatile alternative, paving the way for broader applications in heritage conservation and structural monitoring.