# From Field Archaeology to Virtual Reconstruction: A Five Steps Method Using the Extended Matrix
## 4 Materials
### Onde Marine, Necropolis of Banditaccia (Cerveteri, Italy)  
Within the collaboration--started with the European 3D-ICONS project ([http://3 dicons-project.eu/](http://3 dicons-project.eu/) (accessed on 26 May 2021))--between the Soprintendenza Archeologia del Lazio e dell'Etturia Meridionale and CNR-ISPC (former ITABC) for the use of innovative methodologies for the study and valorisation of the Banditaccia Necropolis, a large number of 3D survey and documentation activities was carried out [31]. One of the most important was performed in 2015 in the Necropolis of Banditaccia (Cerveteri) and was focused on the archaeological excavation of the tombs 2074-2072. Three unpublished burial chambers were found on the site, one of which was featured by bi-coloured painted decorations (red ochre and black). The 3D model, obtained by terrestrial photogrammetry and by UAV, was conceived both for technical (orthophotos, plans and sections at an archaeological scale--1:20 and 1:50) and communicative outputs (immersive head-mounted display, natural interaction, projection mapping). For this reason the 3D model was acquired with image-based technology in order ensure an high visual resolution and allowing a detailed characterisation of the wall surfaces (1 px/mm texture) [23].  
In order to obtain a virtual reconstruction of the funerary structures of the Onde Marine context, archaeological evidence was analysed and discussed with experts in the various archaeological, historical and architectural issues. This task was performed in Blender through the EMtools addon (see _infra_ Section 5.2) by connecting the stratigraphic record collected on the field and formalized in the Matrix of Harris (through the yEd graph editor and a GraphML file format) with the proxy representation (see Figure 5). In our experience, this process enhanced the general comprehension of the transformation of the site (construction, phases of use of the necroolis, destruction of the site, activities of grave robbers etc.) resulting in a better interpretation of the site. After devising a stratigraphic analysis, the first reconstructive draft (proxy model) was elaborated by integrating the mounds of the missing parts and then adding architectural details (see _infra_ Figure 6).  
The 3D reconstruction of the mounds and their context was made using the digital replica of the site as a metric reference. In this way it was possible to progressively proceed with the reconstruction by displaying the two models in parallel, verifying dimensions, orientations and elevations and graphically visualising the relationship between the stratigraphic data (US/USM) and the virtual one (USV). Starting from geometric primitives or by extruding two-dimensional profiles obtained from drawings, the structures were progressively refined by adding details with digital sculpting operations and finally by assigning shaders and textures that simulated the materials in order to give the reconstruction a realistic appearance (representation model - RM). Based on the process described above, it is possible to represent the site through three different views: the digital replica, the proxy model referring to different degrees of reconstructive reliability and, finally, the representation model (see Figure 7).  
Figure 4: Virtual reconstruction of the Temple of Mars Ultor in the Forum of Augustus. Above: the examples shows different model created within this project: (**a**) Actual model; (**b**) Reconstructive model (only volumes); (**c**) Representation model (geometry, shaders and textures). Below: example of the first 4 steps of the EM workflow applied on a column of the _porticus_: (**1**) Digital replica and data collection; (**2**) Data management and analyses; (**3**) Interpretation and virtual reconstruction (proxy model) (**4**) representation model. See colour chart in Table 3.