1. a International Institute for Geo‐Information Science and Earth Observation (ITC) , Hengelosestraat 99, PO Box 6, Enschede 7500 AA, The Netherlands
2. b GEOSYS Recherche & Méthodologies, 20 , Impasse René Couzinet Parc de la Grande Plaine – BP 65815 , 31505 Toulouse cedex 5