Abstract
Highly accurate 3D micro topographic mapping in mountain research demands for light equipment and low cost solutions. Recent developments in structure from motion and dense matching techniques provide promising tools for such applications. In the following, the feasibility of terrestrial photogrammetry for mapping topographic location properties of sparsely vegetated areas in selected European mountain regions is investigated. Changes in species composition at alpine vegetation locations are indicators of climate change consequences, such as the pronounced rise of average temperatures in mountains compared to the global average. Better understanding of climate change effects on plants demand for investigations on a micro-topographic scale. We use professional and consumer grade digital single-lens reflex cameras mapping 288 plots each 3 x 3 m on 18 summits in the Alps and Mediterranean Mountains within the GLORIA (GLobal Observation Research Initiative in Alpine environments) network. Image matching tests result in accuracies that are in the order of millimetres in the XY-plane and below 0.5 mm in Z-direction at the second image pyramid level. Reconstructing vegetation proves to be a challenge due to its fine and small structured architecture and its permanent movement by wind during image acquisition, which is omnipresent on mountain summits. The produced 3D point clouds are gridded to 6 mm resolution from which topographic parameters such as slope, aspect and roughness are derived. At a later project stage these parameters will be statistically linked to botanical reference data in order to conclude on relations between specific location properties and species compositions.
Highlights
Vegetation on mountain summits is under pressure
The aim of this paper is to show the possibilities of close-range photogrammetry of local elevation model production for micro topography analysis
Vertical images of the plots are captured using a pole with a digital single-lens reflex (DSLR) camera attached held at approximately two metres height above the plots (Figure 3)
Summary
Vegetation on mountain summits is under pressure. Due to rising temperatures in mountain areas there is a change in species composition on mountain summits. Research has shown that species are shifting towards higher altitudes, which leads to an increase in species richness on boreal and temperate summits, whereas there is a species-loss on Mediterranean summits (Pauli et al 2012). High-elevation species, endemics in particular, are put under pressure by the rising temperature and through increasing competition. Species that are not able to adapt or to migrate may go extinct, at least locally. Steep elevation gradients and fine-grained roughness of terrain, especially, may present refugia for cryophylic vegetation and mitigate the effects of rising temperatures (Scherrer & Körner 2010)
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