## 4 Conclusions  
The investigations conducted using two laser technologies developed by the Diagnostic and Metrology Laboratory (DIM) of the ENEA research centre in Frascati, inside the House of Diana in Ostia Antica, have provided complementary results and information: the RGB-ITR scanner created 3D-coloured models of two rooms of the House and the LIF systems produced 2D compositional maps of the surfaces, which were used as an additional texture of the 3D models. This combination allowed the creation of easily readable and visually engaging virtual objects of the House: 3D models with real and/or enhanced colours that help extract details of the decoration, which are almost completely lost. These models were enriched with additional textures providing chemical information on the substances constituting walls, ceilings, and decorations, thereby offering insights into the historical phases of the building. In particular, the method used was able to document the masonry structure of Room A and of the north and west walls of Room B, which resulted in showing the various transformations that have affected the building over the centuries. The analyses highlighted the presence of different materials relating to two distinct phases. Regarding the masonry in both Room A and Room B, the different fluorescence responses of the binder used in the mortars made it possible to distinguish the portions of the original masonry from those that were reconstructed or remodelled later. These transformations, which are hardly legible to the naked eye, are clearly revealed in the fluorescence images and can be precisely located thanks to the ability to use the LIF maps as textures of the 3D model created by RGB-ITR. As for the paintings, moreover, LIF revealed materials not visible to the naked eye, in particular traces of consolidating and protective agents. On the surfaces, these must be related to the conservation interventions carried out between 1989 and 1990, which involved the counter-detachment of the paintings, their repositioning on panels in materials that were innovative at the time, and the treatment with organic fixatives. The latter, however, have over time altered the legibility of the paintings. It is probably no coincidence that the protective and consolidating agents have been identified in particular in correspondence with the most valuable figurative elements, which, nevertheless, are today scarcely legible. The results of the analyses carried out on the ceiling of Room A highlighted the presence of synthetic polymeric resins different from those detected on the wall paintings, and in much higher concentrations. These results appear to be consistent with the complex conservative history of the building, whose fragments, found in collapse, were painstakingly reconstructed on concrete supports in the 1970s and later replaced in the 1990s by more innovative honeycomb panels. In conjunction with the ability of LIF to discriminate between different classes of materials, however, the limitations of this technique in identifying individual materials within the same class with precision are to be noted. For the future, therefore, measurements on some interesting spots of masonry and decoration with more selective analytical methods are desirable; they could provide complementary data of greater detail from the chemical point of view, that could be useful as reference data with further LIF imaging measurements in Ostia context. The work has, in this way, on one hand, demonstrated the capability of the combined use of LIF and RGB-ITR scanners, on the other hand, it has provided valuable historical information about an important complex without requiring any sampling, scaffolding or long processing time, ensuring a reduction in analysis and monitoring times and costs. Furthermore, thanks to the fact that they are not influenced by ambient lighting conditions, the presented sensors can also be used on masonry and painted surfaces stored in different contexts, for example outdoors.