Image-based modelling approach to the documentation of Crvenkuša cave site

Archaeological excavations at the cave complex Crvenkuša – Tamnica – jama Suhi Rumin were conducted in the fall of 2018 as part of the HRZZ funded project „Where East Meets West – the Cetina River Valley as an Ancient Pathway of Communication (Cetina Valley Survey)“, led by prof. dr. sc. Helena Tomas. Although surface pottery was identified as dating back to the early Neolithic impresso culture, subsequent excavation has shown a mixture of archaeological material from various time periods, which points to the secondary context of the finds. The documentation process regarding cave sites follows an established practice where the location of the trench is shown in both a topographical ground plan of the cave and a cross-section for the visualization of elevations. The metric data needed for the generation of these plans is usually collected using simple laser distance meters or tape measures, with the level of detail determined by the surveyor, who takes measurements at a smaller or a bigger interval. The resulting two-dimensional documentation is therefore to some extent subjective, as the person recording the data determines the level of detail needed. 3D recording of cave sites provides a much more objective dataset for the reproduction of plans but has until recently been limited to the use of terrestrial laser scanners which by the nature of their design work very well in low light environments. On the other hand, the use of image-based modelling is heavily dependable on the amount of light available inside the caves. In our case study, a combination of natural light and minor artificial light sources provided us with nearly ideal conditions to test out the utility of photogrammetric 3D models for the documentation of cave excavations. The results of our case study will be presented in the context of past documentation methods and potential problems regarding documentation of cave sites using image-based modelling.