1. a Department of Geography , University of Maryland , 2181 LeFrak Hall , College Park , MD 20740
2. b Geographic Information Science Center of Excellence , South Dakota State University , Brookings, SD 57007
3. c European Commission – DG Joint Research Centre , Institute for Environment and Sustainability , Land Management and Natural Hazards , INFOREST Project , Via E. Fermi, TP 261 , Ispra (Va), I‐21020, Italy