Measuring Smooth Stone: Effects of Surface Texture on SfM Photogrammetry and Handheld 3D Scanning for Ancient-Vessel Metrology

The accuracy of 3D digitisation methods is strongly influenced by the surface properties of the observed object, particularly its texture, reflectance, and material structure. This is especially relevant to the systematic metrological analysis of ancient stone vessels undertaken by the Artifact Research Foundation, where high-resolution 3D models are increasingly used for geometric analysis, including through dedicated tools such as Petrie Scope. This study assesses the potential influence of crystalline granite texture on residual dispersion in Structure-from-Motion (SfM) photogrammetry and handheld laser-triangulation scanning using granite metrological reference objects measured under controlled conditions before and after application of a self-sublimating scanning spray. For the unsprayed cube, the pooled empirical 99% residual interval was −33.8 to +33.1 µm for photogrammetry and −49.9 to +54.5 µm for handheld scanning; for the unsprayed cylinder, the corresponding intervals were −51.6 to +30.7 µm and −76.3 to +55.3 µm. Sprayed reconstructions in the principal comparison exhibited lower residual dispersion and circularity RMSD. Repeated handheld-scanner acquisitions supported this trend, while supplementary SfM analyses demonstrated the influence of camera-network configuration and calibration treatment on surface-residual dispersion. By linking surface residuals to circularity and centre-offset descriptors, this study provides an empirical basis for interpreting geometric regularity in ancient stone vessels. The results for the tested granite surfaces and workflows highlight the need to distinguish measurement-induced deviations from genuine manufacturing irregularities when analysing polished stone artefacts and ancient vessels.