Three-dimensional survey of guattari cave with traditional and mobile phone cameras

Sometimes, the georeferencing of a cave in the global reference system can be challenging. Some difficulties may arise when narrow passages do not allow the use of classical topographic equipment or a terrestrial laser scanner. In these specific cases, the surveyor can employ a visual-based approach to produce both the followed path and the 3D model of the hypogeum. The report we are presenting is the result of a survey in the Guattari cave carried out using images taken by a Huawei P9 mobile phone and a Nikon D800E camera with a 16mm fisheye lens. Several targets were measured in order to contain the deformation of the models. Three GCPs located just outside the cave have been used to georeference the models. The data have been acquired by a double frequency GNSS receiver in static session mode. The comparison between the two models shows a substantial concordance only in the area outside the cave where the GCPs were measured. In the innermost areas, the two models differ by as much as two meters.