Virtual Outcrops Building in Extreme Logistic Conditions for Data Collection, Geological Mapping, and Teaching: The Santorini's Caldera Case Study, Greece

In the present work, we test the application of boat-camera-based photogrammetry as a tool for Virtual Outcrops (VOs) building on geological mapping and data collection. We used a 20 MPX camera run by an operator who collected pictures almost continuously, keeping the camera parallel to the ground and opposite to the target during a boat survey. Our selected target was the northern part of Santorini's caldera wall, a structure of great geological interest. A total of 887 pictures were collected along a 5.5-km-long section along an almost vertical caldera outcrop. The survey was performed at a constant boat speed of about 4 m/s and a coastal approaching range of 35.8 to 296.5m. Using the Structure from Motion technique we: i) produced a successful and high-resolution 3D model of the studied area, ii) designed high-resolution VOs for two selected caldera sections, iii) investigated the regional geology, iv) collected qualitative and quantitative structural data along the vertical caldera cliff, and v) provided a new VO building approach in extreme logistic conditions.