Abstract. In this paper the ETM+ sensor of Landsat-7 is used to discriminate soils developed on materials with marls and gypsums in the Southeast of the Community of Madrid (Spain). The gypsisol distribution, their bright colours, the scarse vegetal coverland and the high level of erosion let both a visual and a digital discrimination as opposed to other covers and materials. In this respect the ETM+ images are useful to study soil variability in semi-arid environments, although is very difficult discriminate soil units. To accomplish the present research work, a visual analysis has been carried out (through various spectral band convinations, spectral and radiometric enhancements), together with a digital analysis and a supervised classification through minimum distance criteria.
Key words: Remote sensing, Landsat-7 ETM+, gypsisols.