1 Institute for Digital Communications, School of Engineering, University of Edinburgh, Edinburgh EH9 3FG, UK. Electronic address: S.Tsaftaris@ed.ac.uk.
2 Pattern Recognition and Image Analysis (PRIAn), IMT School for Advanced Studies, Lucca 55100, Italy.
3 Institute of Bio- and Geosciences: Plant Sciences (IBG-2) Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.