Development of land degradation spectral indices in a semiarid Mediterranean ecosystem - Chabrillat, S; Kaufmann, H; Palacios-Orueta, A; Escribano, P; Mueller, A; Ehlers, M; Posa, F; Kaufmann, HJ; Michel, U; DeCarolis, G (Proceedings of SPIE - The International Society for Optical Engineering, 2004)