Articles by Mauro Cremaschi

Digital documenting of archaeological evidence represents a crucial tool in the study, preservation, management, and promotion of archaeological sites in remote regions and in fragile landscapes. In fact, in marginal environment, the knowledge related to archaeological heritage can quickly disappear, especially when policies to protect cultural heritage are unreliable or lacking. In the last few decades, archaeological fieldwork has seen the increasing use of Structure-from-Motion (SfM) photogrammetric technique as a tool for mapping and recording archaeological evidence. This technique allows the creation of highly detailed 3D models of archaeological sites, monuments, and artefacts from sets of simple but accurately taken pictures, thus preserving the data for further research or (digital) cultural valorisation. Nowadays, low-cost/commercial off-the-shelf sensors (professional and semi-professional digital cameras and smartphones as well) are widely available and accessible by most of the users operating in cultural heritage documentation. This has made the acquisition of field pictures in archaeological research much more flexible and cost-effective. 3D models obtained from these pictures through photogrammetric commercial software can be scaled with a known-measure providing highly detailed models for archaeological purposes. This enhances the ability of archaeologists to record archaeological features during field surveys and rapidly obtain 3D models. This is especially useful in the case of archaeological surveys carried out in remote and barely accessible areas. In this paper, we present the results of the application of the above-mentioned methods during archaeological surveys in the Sultanate of Oman, where several archaeological features have been recorded through SfM photogrammetry using commercial devices and portable scale-bars. We demonstrate that this is a highly-flexible and fast process to record archaeological heritage in low-accessible or fragile contexts, where a 3D model (with centimetric precision) represents a valuable dataset for further in-lab analysis and cultural dissemination.

This paper illustrates preliminary results of the research project “An inventory of the Terramare in the central Po plain: physiographic context, stratigraphic and structural characteristics, state of preservation”, part of the Cultural Heritage Special Project, promoted by Italian National Research Council. The project involves GIS and remote sensing applications in order to integrate different 2D-3D georeferenced data (sites, excavations, surveys, landscape and territorial data) such as: a) raster data (aerial photographs of different periods starting from 1950, regional cartography, DEM); b) vector data (cartography, thematic layers, archaeological sites, etc.); c) a DEM created by cartographic contour lines and using a total laser station on the ground; d) alphanumeric data (excavation databases, territorial databases). The methodological approach has been to represent and analyse archaeological data from micro-scale (intra-site) to macro-scale (inter-sites), in particular exploring the perspectives of 3D GIS visualisations. Attention was therefore concentrated on the topographical reconstruction of microrelief in relation with the aerial photos (of different periods) used as textures, geomorphological features and archaeological data. We can define this kind of processing as a visualisation of an invisible landscape, as much more information can be retrieved from the terrain than using traditional techniques (aerial photo-interpretation, survey, etc.); in many cases this is very useful in order to help plan an excavation. Regarding the acquisition and processing of multi-temporal, multi-layer and multi-dimensional data, this research deals with a large-scale detailed study of the data collected by topography, but enhanced by surveys and acquisition of data on the ground. In fact one of the main tasks of our project is the creation of detailed models on the basis of the microrelief.

Analysis of site formation processes is a field of research which can be enhanced by means of computer applications. In this paper, the authors suggest the use of image analysis applied to the study of soil micromorphology and to archaeological deposits, aimed at the qualitative and quantitative evaluation of the soil components. The presence of specific devices and software allow these problems to be faced in a quick and user-friendly way, thanks to the Windows interface. The case study looks at the Uan Afuda cave in the Tadrart Acacus (Libyan Sahara), and the sediments related to the Mesolithic occupation (8900-8000 BP), which is characterised by vegetable accumulations alternating to ashes layers. The application let us weigh the specific components of the layers, from both a microscopic (soil thin sections) and macroscopic (excavated stratigraphic section) level. Consistence of results opens up new perspectives of analysis for the comprehension of the formation processes in arid environments and for the cultural problems linked to them.

S. Rosa terramara, which measures 7 hectares, is a Middle and Recent Bronze age site, excavated since 1984. Cooperation between archaeologists and geologists has made it possible to experiment with the comparative analysis of computer image processing of the aerial photos, integrated with the detailed study of a DTM (Digital Terrain Model), in particular in relation to the geopedological and geoarchaeological interpretation of the site. The integration of two kinds of data, aerial photographs and a DTM, has been complemented by the texture mapping of the aerial photo overlaid on the corresponding 3D model. Significant ranges in the pixel distribution in the digital aerial image identified four main areas; any area presents particular digital features. For example, the digital features of the small village are very different from the characteristics of the large and more recent village. The digital classification of these areas identified the following: area 1, alluvial sediment (posthumous) which hides part of the earthwork; area 2, the nucleus of the small village; area 3, the diking of the big village; area 4, a Roman villa (another posthumous event). The final interpretation, after processing, distinctly shows the formation of natural (vertisoils) and artificial deposits (earthworks). In particular in the north-western area of the aerial photograph the interruption of the diking means that in that point the structures are buried because of a flood. Moreover, it results that the two villages are separated by a large ditch. On the basis of these results it has been possible to reconstruct the evolution of the site and of the environment in different periods: 1) the site before the Bronze age; 2) the terramara in the Middle Bronze age; 3) the terramara in the Recent Bronze age; 4) the site in Roman age; 5) the site in Medieval age. The computer processing, integrated with the aerial photo-interpretation, shows an important series of data not obtainable through traditional techniques. The construction of the DTM, the texture mapping and the digital image processing have clearly enhanced the shape of the structures of the terramara as well as the stratigraphical excavations. This also resolves the problems which emerged in the aerial photo interpretation. In particular, the interruption of the earthwork of the big village in the northern area seems connected with the burial of part of the anthropic structures, after the abandonment of the terramara. In conclusion, the computer image processing, together with the DTM and the texture mapping of the site, is an exportable tool, useful for an evaluation of the state of preservation of the Bronze age deposits in the Po valley. These results were obtained without excavation, using only simple stratigraphical surveys on the ground.