3D laser mapping and dynamic visualisation of the Domica cave, Slovakia
1Hofierka, J.; 2Gallay, M.; 3Kanuk, J.
1PAVOL JOZEF SAFARIK UNIVERSITY Email: firstname.lastname@example.org
2PAVOL JOZEF SAFARIK UNIVERSITY Email: email@example.com
3PAVOL JOZEF SAFARIK UNIVERSITY Email: firstname.lastname@example.org
Recent developments in the laser scanning technology provide new tools and methods for a very accurate and cost-effective way of mapping complex volumetric landscape features such as caves. It is difficult to map such 3D features using traditional surveying methods without a large loss of detail. Also, the extreme environmental conditions in the cave (darkness, water, moisture, or mud) make the mapping very challenging. In this work, we have collected terrestrial laser scanning (TLS) data coupled with airborne laser scanning (ALS) data to build a volumetric, 3-D model of the Domica cave area in Slovakia. The total length of the scanned cave corridors is about 1.5 km. The terrestrial mapping was done using a Faro 3D laser scanner resulting in 5 billions of points acquired from 330 scanner positions. The total accuracy of registering the individual point clouds into a single cloud and, further, in the Slovak national coordinate system reached 12 millimetres at 1 sigma. The terrain above the cave contributes to the development of the cave system via a complex interaction between flowing water and the subsurface limestone rock forming the cave. The ALS data were acquired in August 2014 with a Leica ALS-60 scanner. The achieved average point density on the ground is between 0.5 to 6 points per metre squared depending on the land cover (i.e. forest, grass land, scrubs). The ALS data were filtered and processed to derive a digital elevation model (DEM) and a digital surface model (DSM) of the area in the form of a raster. Spatial interpolation and geomorphometric methods were used to identify specific karst geomorphic features such as sinkholes in the forested area. In order to generate a 3D surface model of the cave system from the TLS points, we decimated the original dataset and we used it to generate a mesh. The work flow for both ALS and TLS data processing was based on open-source software. Combining the TLS and ALS data resulted in a 3D model of the area supplemented by several landscape component data and factors potentially contributing to the development of the cave system (water flow routing, temperature, moisture in the cave). To better understand the functioning of the cave system and dynamics of the spatial processes we have used several visualisation methods to represent the cave system of the area including volumetric, isosurface and dynamic (fly-through) visualisation methods.
laser scanning; cave; visualization