1. a Institute for Electromagnetic Remote Sensing of the Environment, National Research Council of Italy (CNR-IREA) , 20133 , Milano , Italy
2. b Institute of Intelligent Systems for Automation, National Research Council of Italy (CNR-ISSIA) , 70126 , Bari , Italy
3. c Environmental Engineering and Sustainable Development Department , Technical University of Bari , 70125 , Bari , Italy