Il rilievo del riparo Bombrini: tecniche di fotogrammetria SFM ed analisi di densità per la gestione 3D di un contesto di scavo

The topographic survey at Riparo Bombrini: using sfm photogrammetry and density analyses to manage 3D data from the excavation - This paper focuses on some spatial analyses performed on the dataset collected from the “Riparo Bombrini” in the Balzi Rossi archaeological area (Liguria, Italy). Documented during several campaigns using non-digital techniques, the excavation area has been surveyed in 2017 using a completely open source SFM photogram- metry operating chain (Python Photogrammetry Toolbox GUI for the point cloud computing and Meshlab for the mesh creation) and all the paper works relating to the positions of the findings has been digitized in a spreadsheet (LibreOffice Calc) and then imported into a GIS environ- ment (QGIS). The positioning of all the findings in a GIS allowed us, for the first time since the beginning of the project, to start planning our post- excavation spatial analyses: the excavation area has been divided into a 10 cm squares grid and a presence/absence raster has been created (the cell value ranging from 0 to 18 findings). A second, and more appealing, approach tested has been the density analysis one: first a set of raster has been interpolated using the Nearest Neighbour algorithm for each archaeological horizon and then the KDE algorithm has been applied to the same dataset to create a second set of raster. The comparison between the two sets of raster clearly shows how the KDE algorithm (available both in ArcGIS and in QGIS) gives a more immediate visual perception of the different clusters of findings. Since the excavation is still on-going it is too early for any other analysis but the simple test of the methodol- ogy, but the ability shown to highlight any clustering of our findings is more than promising.