1. a Department of Forestry , Instituto Superior de Agronomia , Tapada da Ajuda, Lisboa, 1349-017, Portugal E-mail:
2. b Cartography Centre , Tropical Research Institute , Travessa Conde da Ribeira 9, Lisboa, 1300-142, Portugal E-mail:
3. c Divis@o de Sensoriamento Remoto , Instituto Nacional de Pesquisas Espaciais , Av. dos Astronautas 1758, S@o José dos Campos, CEP 12227-010, SP, Brazil E-mail:
4. d Global Vegetation Monitoring Unit, Space Applications Institute , Joint Research, Centre , TP. 440, Ispra, I-21020, (VA), Italy E-mail: