1. a Remote Sensing Laboratory , University of Valladolid , Dp. Applied Physics , Faculty of Sciences , 47071‐Valladolid , Spain
2. b Remote Sensing Laboratory , INIA , Ministry of Education and Science , Crta. ha Coruña , km. 7.5, 28040 Madrid , Spain
3. c EUIT Forestal , Universidad Politécnica de Madrid , Avda. de Ramiro de Maeztu s/n , 28040 Madrid , Spain