Abstract
Abstract. The survey of ancient cave can generally be performed by traditional topographic methods that allow also its georeferencing in a global reference frame; some difficulties may arise when there are narrow tunnels that do not consent the use of a total station or a terrestrial laser scanner. In such cases a visual-based approach can be used to produce, both the followed path and the 3D model of the hypogeal environment. A prompt photogrammetric survey has been used to reconstruct the morphology of the La Sassa Cave, situated in the municipality of Sonnino (Latina), in the lower Lazio region. In this cave, a very large quantity of Pleistocene animal bones was found, together with several fragments of Copper Age human bones and Bronze Age impasto potsherds. The survey was carried out using a DSLR full frame camera Nikon D800E with a Nikkor 16 mm fisheye lens pre-calibrated. During the acquisition, several targets were measured in order to contain the deformations model. The photogrammetric model has been georeferenced using 3 GCPs positioned outside the cave entrance where a double frequency GNSS receiver has acquired data in static session mode.
Highlights
Cave environment is generally characterized by lack of light, flowing water, high humidity, limited space, and complex morphology, so its mapping is a challenging task that has traditionally been undertaken by topographic surveying methods, traverse method for establishing cave survey lines is a mature and effective one (Gallay et al, 2015)
The survey of ancient cave can generally be performed by traditional topographic methods that allow its georeferencing in a global reference frame; some difficulties may arise when there are narrow tunnels that do not consent the use of a total station or a terrestrial laser scanner
When the modeling has to be added to the mapping operations the methods to be used must be automatic in order to prevent the possibility that important details can escape from expert analyses. 3D models created from terrestrial laser scanning (TLS) and close-range photogrammetry offer an alternative solution or at least a valuable supplement to traditional cave survey. 3D models are often both faster to produce than a sketch and even more informative
Summary
Cave environment is generally characterized by lack of light, flowing water, high humidity, limited space, and complex morphology, so its mapping is a challenging task that has traditionally been undertaken by topographic surveying methods, traverse method for establishing cave survey lines is a mature and effective one (Gallay et al, 2015). It is necessary to adopt a survey method which is able to provide the most detailed description of the hypogeal environment, independently from the operator's choices. 3D models are often both faster to produce than a sketch and even more informative Those models can provide cross-sections anywhere, and all this information is obtained in a non-subjective manner which is unbiased and scientifically repeatable (Jordan, 2017). Accurate LIDAR systems utilize infrared remote sensors capable of scanning hundreds of thousands of points per second, in total darkness. This technology is very expensive and problematic (or impossible) to use in confined spaces and narrow passages
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