1. Research Group for Earth Observation, Department of Geography, University of Education, 69115 Heidelberg, Germany
2. Department of Geosciences, Soil Geography & Soil Science, University of Cologne, 50923 Köln, Germany
3. Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, 14473 Potsdam, Germany
4. now: Deutsches GeoForschungsZentrum GFZ, Telegrafenberg A43, 14473 Potsdam, Section 4.2