The survey of the ‘precious ones of Constance’. Tools and techniques for three-dimensional restitution of complex surfaces at sub-millimetre resolution

Abstract

The digital reproduction of cultural artefacts is a challenging task and should not be underestimated today. The great variety of objects and the complexity of textures that characterise them inevitably necessitate the delineation of even more precise and specialised studies. Numerous factors must be managed to ensure high quality and accuracy of submillimetre resolution models. The key issues concern the purpose of the survey and the associated data dissemination, timing, instrumentation and expertise available. In addition to the listed aspects, there are inherent typological factors of the wide and diversified cultural heritage: specific and unique characteristics of each artefact – related not only to the small size, but also to the constituent material – cause even more reproducibility difficulties, due to reflective, translucent and/or excessively homogenous surfaces [1]. Lastly, the boundary conditions in terms of the opportunity to work in controlled environments and to move artefacts freely. This study reports two examples of surveying objects of accentuated complexity: “the precious ones of Constance” (Figure 1). These are emblematic cases selected to determine whether the recording systems chosen, a structured light scanner and a low-cost camera integrated into a USB microscope, could support the requirements of accurate and reliable three-dimensional reconstruction. The first one is the Crown of Constance of Aragon, the second one is a couple of earrings, the so-called earrings “of Costance”.