One of the most common techniques for surveying architectural heritage today is the laser scanner. With this technology a point cloud is obtained which, after being processed by computer, results in a geometric mesh, and ultimately a three-dimensional model. But laser scanning delivers also, as a byproduct, the value of the reflectance of the documented surfaces, which is the quotient of the energy of the emitted laser beam (by the machine) divided by the energy received after being reflecting on the surface of the measured object. This value varies according to the angles of incidence and reflection of the beam, but also on the optical and surface properties of the materials on which the laser light is reflected. This latter characteristic has led to hypothesize that the different materials that compose the surveyed surface can be individualized and automatically recognized. After studying similar cases in the scientific literature (made with natural light, with flights and LIDAR, etc.) we have tried to see if this assumption could be confirmed experimentally, with promising results. In this work, we explain the evidence and the methodology of the experiments performed to test the validity of this hypothesis.
Sola-Morales, P.; Toldrà, J.M.; Puche, J.M.; Macias, J.M.; Fernández, I.; (2017). Automatic recognition of materials from laser-scanner survey data by the reflectance method. Proceedings of the 3rd International Conference on Preservation, Maintenance and Rehabilitation of Historical Buildings and Structures, Braga-Portugal 14-16 June. Pages 29-37.