Close-range photogrammetry reveals morphometric changes on replicative ground stones

The pursuit of a quantitative approach to functional analysis of stone tools is an ongoing endeavour for traceologists. Technological advancements in 3D imaging techniques, such as photogrammetry/3D scanners, CT scanning, 3D digital microscopy, confocal microscopy, AFM and FEG-SEM and micro-topographical scanning, have greatly facilitated the detailed capturing of the geometry and surface texture at multiple levels of observation, from the object-scale to the nano-scale. However, while such technological innovations have predominantly focused on flaked assemblages, ground stone tools have only recently begun to receive due attention, and a standardised protocol for their study is yet to be established. In order to comprehend the function(s) of these tools, analytical techniques that enable a 3D visualisation of the entire item and the wear affecting the used surfaces have proven to be of great support. To this end, an analytical procedure was developed and tested on slabs and pebbles in order to replicate the use-wear traces observed on Upper Palaeolithic tools. The purpose was to assemble a site-specific reference collection tailored on the artefacts from the cultural level III of the Brînzeni I cave in north-west Moldova. Experimental replicas were used to treat different plant organs during controlled sequential experiments. The present article reports on the analysis based on photogrammetric data acquired during two stages of replicative usage. We tested multiple acquisition setups and elaborations to assess the geometry modification and the surface depletion. By exploring various acquisition strategies, a critical evaluation of potential sources of bias in data collection and subsequent elaboration were performed, and the methodology was accordingly adjusted thereby enhancing the reliability and reproducibility of the results. This study highlights the importance of carefully considering the acquisition strategy in archaeological related research to ensure accurate analyses and to validate robust interpretation.