MAPPING VERTICAL CLIFFS – EXPERIENCES FROM THE DOLOMITES MOUNTAINS –

The article reports the challenging work of 3D surveying and accurately modeling the “Tre Cime di Lavaredo”, often considered the icon of the Dolomites. They fully represent, with their shapes and colors, the concept itself of the UNESCO's site. The 3D recording is based on a fusion of oblique airborne and terrestrial laser scanning, in order to survey all the relief complex, focusing especially on the vertical cliffs. Aerial and terrestrial high-resolution images are also employed for texture mapping purposes. Results of the produced high-resolution photo-realistic 3D model are presented and discussed. Figure 1: The “Tre Cime di Lavaredo” (Three Peaks / Drei Zinnen), an icon of the Dolomites (NE Italy). Introduction The Dolomite mountains (NE Italy) have been declared a UNESCO World Heritage Site in 2009. It features some of the most beautiful mountain landscapes anywhere, with vertical walls, sheer cliffs and a high density of narrow, deep and long valleys. This is particularly true for the “Tre Cime di Lavaredo” (Three Peaks or Drei Zinnen), often considered as one of the “trademark” symbol of the Dolomites as they fully represent with their shapes and colors the icons of the UNESCO's site. The vertical dimension of these and similar mountain complexes are usually unmapped and poorly resolved in a cartographic “nadir-dominated” world. The goal of the project called “Peaks-3D” is the highly detailed 3D surveying of the “Tre Cime di Lavaredo” (and other similar rock complexes), especially their vertical cliffs, nearly 600 meter high, for digital documentation and conservation, geological and geomorphological analysis, tourism and communication purposes, 3D mapping of the ascent roots, etc. The digital recording of the current situation and the monitoring of ongoing processes are fundamental prerequisites for analyses and establishment of sustainable measures of protection. The 3D surveying of the “Tre Cime di Lavaredo” is based on a fusion of oblique airborne and terrestrial laser scanning. Aerial (nadir and oblique) and terrestrial high-resolution images are also employed for texture mapping purposes. 3D surveying and modeling works, based on the integration of aerial and terrestrial LiDAR data are presented in Ruiz et al., (2004) and Boehm & Haala (2005) respectively for steep terrain modeling and 3D city modeling. Landslide monitoring is presented in Sturzenegger et al., (2007), Szekely et al. (2009) and Squarzoni et al. (2009). Gruen & Murai (2002) reported the image-based 3D surveying and modeling of Mount Everest for cartographic and mapping applications. In the next sections the 3D recording campaign with the achieved results of the realized high-resolution photo-realistic 3D model are presented and discussed. 3D recording campaign The 3D surveying was firstly attempted with a traditional aerial photogrammetry approach, combined with some terrestrial laser scanning (TLS) acquisition to overcome some occlusions of the aerial views. After the first photogrammetric results, we realized that the available images were not ideal for the automated DSM generation and so an oblique LiDAR flight was performed and integrated with the TLS data. Terrestrial images were also acquired, both in the visible and IR domain, for photo-realistic visualization of the final 3D model and further thermal analyses of the geological structures. Photogrammetric surveying Photogrammetry is able to derive metric and accurate 3D results at various scale of applications and aerial photogrammetry is the primary source for mapping and cartography. For the 3D recording and modeling of the “Tre Cime di Lavaredo”, a dedicated photogrammetric block was flown on September 2004 by CGR Parma (Italy) using a Wild RC30 camera with a 153 mm lens and 60% forward overlap (Figure 2a).