## 5 Data Collection in IVR and Following GIS Data Analysis  
The 3D tiled model resulting from photogrammetry is processed into a form to allow optimized loading at runtime into GeaVR; such a form contains multiple meshes as well as physics calculations. For the same reason, surface texturing files are converted into an optimized format such as Microsoft  
Figure 8: (**a,b**) Original photos scanned at 1600 dpi; (**c**) orthorectified model that was created using six Ground Control Points (GCPs) (blue triangles) and 116 automatic generated tie points (green cycle); (**d**) ortho image with pixel size of 1 m; (**e**) final DSM created with pixel size 1 m and accuracy 2 m horizontally and 1 m vertically; (**f,g**) orthomosaic of 1960s stereo images and generated digital surface model of the area, where the excavated area is located. Reference system: WGS84/Geographic coordinates. DirectDraw and DDS surface files. This processing is automatically done using an ad-hoc and drag and drop system, which will be available with GeaVR software. The resulting folder contains all files necessary to load the VR scene to be navigated in IVR, using a user-friendly interface. After the conversion, the produced scene can be loaded (Figure 9) and the first step regarding data collection in IVR is related to the survey of the area, which we tried to explore using all three modes (Figure 4c). Drone modality was finally selected, because it allowed us to rapidly move within the VR scenario, as well as to fly above and around the objects of interest to more effectively map 3D geological features, as shown in Figure 9 and in the following video: [[https://youtu.be/Mw1c2503](https://youtu.be/Mw1c2503) qAo]([https://youtu.be/Mw1c2503](https://youtu.be/Mw1c2503) qAo). After an overall exploration of the mine to identify interesting geological features that cannot be easily appreciated through conversional means, we came up with a list of possibilities as follows (Figure 10):  
* Upper boundary of excavation in the mine area,
* Eruption phase boundaries related to the Minoan eruptions, including measurements of their thickness,
* Areas covered by anthropogenic debris and machineries,
* Areas covered by natural debris flows. Figure 9: Snapshot of survey in Immersive Virtual Reality (IVR) aimed at an overall recognition of the volcanic layers belonging to the Late Bronze Age (LBA) eruption that are exposed in the mine, using the drone navigation mode. To perform these tasks, we used the following tools: Camera, Line, Polygon and Ruler (Figure 4d). With the Line tool, the user can trace a line point by point; the Polygon tool can be used to trace a polygon, always with a point-by-point approach (vertices). Both the lines and polygons created are characterized by a unique ID number and x,y,z location that corresponds to the real-world geographic coordinates, and in addition, short textual information, e.g., a brief note and a name, can be added. All lines and polygons can be exported in KML format, to be directly imported in a GIS environment, whereas information about vertices can be exported as a text file, including z values. The Ruler tool provides the distance between two points selected in the scene and the Camera tool captures a screenshot of user's observation in the IVR scene. Figure 10: Different aspects of the mine’s morphology captured in GeaVR session using orthomosaic created during UAV survey. In each one, the upper boundary of excavation (orange line), the boundary between phases P4 and P2 (blue line), as well as the body of debris flows (yellow line) was mapped. (**a**) Mapping of anthropogenic debris areas and location of screenshots c and d; (**b**) location of machineries found in the mine; (**c**,**d**) anthropogenic debris along with natural debris flows; (**e**) the famous section consisted of eruption phase boundaries; in addition, the debris flow body was mapped. The Line tool allowed us to trace the upper boundary of excavation in the mine area and outcropping boundary between eruption phases P2 and P4 (Figure 10).