3D recording of archaeological excavation: the case study of Santa Marta, Tuscany, Italy

The archaeological excavation is a destructive and not repeatable process: the documentation of archaeological stra-tigraphy and relations between the layers is an essential component of the work of the archaeologist aimed at the understanding the site object of researches. The traditional techniques of documentation, based on direct survey and manual drawing, are time consuming to be executed and they are also characterized by some poor level of precision and accuracy that, spread over time, can lead archaeologist to errors and misunderstandings. The use of traditional techniques of survey does not allow any margin of error in the interpretation: once produced documentation, layers are destroyed and it is hardly possible to make further corrections in documentation. Over the last two decades technological innovations have progressively reduced these issues: survey instruments such as total stations and dGPS have gradually replaced the direct survey. The introduction of digital SLR cameras has eliminated the cost of production of photographs and allowed the archaeologists to produce a massive documentation of contexts, mainly qualitative. The laser scanners have been tested within various excavation sites: the possibility to record excavations in three di-mensions have been found to be of great interest by archaeologists, but the high cost of the instrumentation and the complexity of the whole process of processing and management of laser data have limited its use and dissemination. In recent years, the advent of photogrammetric software based on the ‘Structure from Motion’ technique has gradually made accessible three-dimensional sur-vey within the excavation sites. During the excavation of the roman site of Santa Marta, in Cinigiano (GR), we developed a pipeline for fast 3D recording of excavation. Through an integrated approach of topographic instruments, aerial and terrestrial images, semi-automated photogrammetric packages and GIS system we have been able to systematically recording in tree dimension the stratigraphy of the sites. This approach allowed us to overcome issues related with precision and accuracy of the documentation and different datasets can be integrated to create diachronic 2D and 3D documentation. The high resolution and precision of recor-ded surfaces allow us to improve both quality and speed of documentation, optimizing all the work in excavation site.