Portable Automated Laser Triangulation Scanner for Three-Dimensional Characterization of Cultural Stone Surfaces

Accurate three-dimensional digitization of cultural stone surfaces is important for their documentation and quantitative characterization. This work presents the design, implementation, and experimental evaluation of a portable, low-cost laser triangulation system for the automated digitization of small- and medium-sized stone surfaces. The prototype integrates a motorized positioning platform, interchangeable laser line sensors, embedded motion control, autonomous power supply, wireless communication, and dedicated acquisition and processing software. Static calibration characterized the sensor response in the X and Z coordinates. The Z-coordinate calibration exhibited high linearity over the investigated measurement range (R2=0.999966), with a residual RMSE of 0.497 mm and a maximum absolute residual of 1.248 mm, while the variation in horizontal scale with working distance was described by a Z-dependent calibration function. Laboratory experiments demonstrated the capability of the system to reconstruct surfaces with markedly different topographies and to derive quantitative areal surface parameters according to UNE-EN ISO 25178-2. Honed, sawn, and bush-hammered granite surfaces were successfully reconstructed, with Sa increasing from 0.039 to 0.243 and 0.444 mm, respectively, consistent with the increasing topographical amplitude of these finishes. Polished granite could not be reliably reconstructed because specular reflection interfered with laser-line detection. The results demonstrate the potential of the proposed platform for automated, non-contact three-dimensional documentation and quantitative surface characterization of cultural stone surfaces. Its modular and transportable architecture provides a basis for future field deployment and for adaptation to other applications requiring portable surface characterization.