Geometrical and topological modelling of caves supported by a relational database model

Abstract

Underground caves and their specific structures are important for geomorphological studies. This paper presents a new tool to identify and map speleothems by surveying cave chamber interiors. The chambers were surveyed using a terrestrial laser scanner to obtain point cloud data sets. For the present work, a point cloud of 45 million points collected inside the main chamber of the Algar do Penico (Portugal) was selected. This point cloud was used to generate four 3D-meshes to represent the surface model of the cave chamber with increasing levels of detail. These models are important for geomorphological studies or virtual visits to the cave. The topological and geometrical data of the four models were implemented using the SQLite relational database management. The topological structure supports the implementation of efficient algorithms to help identifying stalactites and stalagmites from the 3D models even for those big data files of higher detail. In this paper, we also present an octree data structure implemented on this database that enables fast spatial queries. Using relational databases to store 3D models of caves, it is also possible to work with several data models simultaneously, in such a way that it is not limited by computer memory resources.