1. a Department of Biometry and Information Sciences , Forest Research Institute Baden-Württemberg , 79100 , Freiburg , Germany
2. b Institute of Photogrammetry and Remote Sensing, Karlsruhe Institute of Technology , 76128 , Karlsruhe , Germany
3. c Institute of Geography and Geoecology, Karlsruhe Institute of Technology , 76128 , Karlsruhe , Germany