1. Department of Environmental Sciences and Land Use Planning; Université catholique de Louvain; Croix du Sud 2 Box 2 B-1348 Louvain-la-Neuve Belgium
2. ICG-4 Agrosphere; Institute of Chemistry and Dynamics of the Geosphere; Forschungszentrum Jülich GmbH; 52425 Jülich Germany
3. Department of Geotechnology; Delft University of Technology; Stevinweg 1 2628 CN Delft The Netherlands
4. TTC -International Institute for Geo-Information Science and Earth Observation; Hengelosestraat 99, PO Box 6 7500 AA Enschede The Netherlands