1. Department of Signal Theory and Communications, School of Telecommunication Engineering, Universitat Politecnica de Catalunya, 08034 Barcelona, Spain
2. American Program in GIS and Remote Sensing, California 15112, Peru
3. Grumets Research Group, Department Geografia, Edifici B, Universitat Autònoma de Barcelona, Bellaterra, 08193 Catalonia, Spain
4. Institute of Geoecology and Geoinformation, Adam Mickiewicz University, Krygowskiego 10, 61-680, Poznan, Poland
5. Department of Forestry and Environmental Conservation, Clemson University, 261, Lehotsky Hall Box, Clemson 340317, SC, USA
6. University of Arkansas Agricultural Experiment Station, Arkansas Forest Resources Center, University of Arkansas at Monticello, Monticello, AR 71655, USA