Built-in smartphone LiDAR for archaeological and speleological research

Abstract

LiDAR technology is reshaping cave surveying by providing detailed 3D models that enhance the accuracy of morphological and rock art digitisation and reduce subjective interpretation. This technology, in its varied forms and solely or combined with other remote sensing techniques such as photogrammetry, enriches the documentation and supports multidisciplinary research by enabling spatial analyses and virtual exploration, thus opening new possibilities in various fields such as archaeology, geology, speleology, tourism or education. In this sense, this research aimed to democratise the use of low-cost mobile LiDAR (Light Detection and Ranging) 3D scanning, subjected to fewer accessibility limitations than tripod-mounted Terrestrial Laser Scanners (TLS), in cave archaeology and speleology. For this purpose, La Pileta Cave in Málaga (Spain) was chosen as a case study. Declared a Spanish National Monument in 1924, the cave boasts one of the greatest collections of prehistoric art in Europe and, therefore, a reference in South Iberia, and outstands out for its varied karstic morphologies. The research methodology involved a systematic process to ensure clarity and accuracy. First, the main itinerary in La Pileta was scanned using the smartphone LiDAR technique. This was followed by a Terrestrial Laser Scanning (TLS) survey of a specific sector within the same itinerary, with numerous morphological details of its karstic environment and important Palaeolithic rock art samples. Both the smartphone LiDAR and TLS spatial data were then validated against a Ground Control Points (GCPs) network previously established using a total station. Given the higher accuracy of TLS for graphical documentation, it was further employed as a benchmark to validate the accuracy of smartphone LiDAR. Despite its limitations, this research revealed smartphone LiDAR as a suitable technique for geometric data recording in cave archaeology and speleology. Solely or combined with TLS, mobile LiDAR can be used to document rock art panels in karstic environments, surpassing the latter technique in terms of texture quality. In addition to the accurate graphic documentation carried out in the cave sector, this research broke down the advantages and disadvantages of the smartphone LiDAR technique and provided a series of recommendations for its use in this context.