## 3 Materials and Methods
### Methods
#### 3.1.4 Geological Applications of 3D Models  
The applications presented here revolve around a series of characteristic elements within the city of _Baelo Claudia_ that we have considered representative of the different working techniques both in the acquisition of data and in the subsequent processing and modelling using GIS (Geographical Information System) environments. The interest lies in obtaining and quantifying parameters related to the deformation and damage suffered during the earthquakes and tsunami that are recorded in the various architectural elements of the Roman city (see, for instance, [14]). In the case of the _Decumanus maximus_, a photogrammetric reconstruction was obtained from the aerial photographs from a flight at 30 m in elevation, from which a DEM (Digital Elevation Model) of 1.5 cm pixels was interpolated. Hillshade elevation models (Figure 5), hypsometric models and the topographic profiles that will be presented later can be derived directly from this DEM. In addition, and in order to obtain partial 3D models of more detailed structures within the _Decumanus maximus_, more detailed DEMs with 3 mm pixels were obtained, capable of perfectly illustrating even the _Decumanus maximus_ tiling and all the structural details of the different existing geological structures. For the tsunami-transported marble dish, the 3D photogrammetric reconstruction obtained in Metashape was exported to KMZ format. This preserved the real georeferencing and textures in ArcGIS Pro, which could be directly photo-interpreted so that the interpretations were registered, georeferenced and dimensioned in 3D. From the interpretation performed, the management of the data obtained in ArcGIS Pro was quite straightforward. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Archaeological Sites** & **Average Error** & \(\mathbf{N^{e}}\) & **Long. Error (m)** & **Lat. Error (m)** & **Alt. Error (m)** & **Error (m)** \\ \hline \multirow{2}{*}{Marble dish tsunami} & Camera & 295 & 0.177 & 0.168 & 0.323 & 0.405 \\  & GCP & 3 & 0.035 & 0.017 & 0.018 & 0.043 \\ \multirow{2}{*}{North City-Wall} & Camera & 221 & 0.25 & 0.32 & 0.29 & 0.51 \\  & GCP & 5 & 0.56 & 0.23 & 0.000 & 0.60 \\ \multirow{2}{*}{Decumanus maximus} & Camera & 350 & 0.27 & 0.56 & 1.75 & 1.85 \\  & GCP & 10 & 0.24 & 0.39 & 0.004 & 0.46 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: This table shows the errors (RMSE) in longitude, latitude and altitude for both the images and the control points of each archaeological site studied. Not only in the archaeosesismological scenarios, but in any current seismic scenario, it is common for buildings to suffer deformations and damage in the walls. These deformations, in many cases, are very characteristic and easily identifiable (e.g., [19; 20]), but given their location in vertical areas and far from the ground, they are difficult to access; therefore, they present difficulties for parameterization and quantification. In addition to this, DEMs are usually obtained (and computed) as elements in \"plan view\", the same as in traditional topography. To apply the full potential of GIS to this type of vertical element, such as walls,  
Figure 5: (**A**) A 3D model of the studied area reconstructing the North City-Wall Bastion from photogrammetry of drone aerial photographs. The overall orientation of the city wall is N162 E and shows strong damage from the earthquake. (**B**) The sense of rotation and axis of rotation of the original elevation points of the east-facing side of the wall in order to soundly operate in a GIS environment. (**C**) Hillshade model of the tilted DEM of the east-facing side of the city wall. (**D**) Map view (elevation view) of the DEM of the east-facing side of the city wall (after tilting); note that a horizontal guide has been added to ease reconstruction.