Mobile LiDAR System: New Possibilities for the Documentation and Dissemination of Large Cultural Heritage Sites

Mobile LiDAR System is an emerging technology that combines multiple sensors. Active sensors, together with Inertial and Global Navigation System, are synchronized on a mobile platform to produce an accurate and precise geospatial 3D point cloud. They allow obtaining a large amount of georeferenced 3D information in a fast and efficient way, which can be used in several applications such as the 3D recording and reconstruction of complex urban areas and/or landscapes. In this study the Mobile LiDAR System is applied in the field of Cultural Heritage aiming to evaluate its performance with the purpose to document, divulgate, or to develop an architectural analysis. This study was focused on the Medieval Wall of Avila (Spain) and, specifically, the performed accuracy tests were applied in the Alcazar gate (National Monument from 1884). The Mobile LiDAR System is then compared to the most commonly employed active sensors (Terrestrial Laser Scanner) for large Cultural Heritage sites in regard to time, accuracy and resolution of the point cloud. The discrepancies between both technologies are established comparing directly the 3D point clouds generated, highlighting the errors affecting the architectural structures. Consequently, and based on a detailed geometrical analysis, an optimization methodology is proposed, establishing a segmented and classified cluster for the structures. Furthermore, three main clusters are settled, according to the curvature: (i) planar or low curvature; (ii) cylindrical, mild transitions and medium curvature; and (iii) the abrupt transitions of high curvature. The obtained 3D point clouds in each cluster are analyzed and optimized, considering the reference spatial sampling, according to a confidence interval and the feature curvature. The presented results suggest that Mobile LiDAR System is an optimal approach, allowing a high-speed data acquisition and providing an adequate accuracy for large Cultural Heritage sites.