ABSTRACT
The term 'scale' is often used ambiguously. When a manager envisages processing a 'large-scale' problem, he implies a vast spatial field. A level of perception corresponds to the tools, methods and estimates employed for detecting a given organisational level. Organisational levels are related to the components of ecosystems, which are of two types, viz., abiotic and biotic. The presence of mixels in remote-sensing data gives rise to errors in pixel-by-pixel classification. In fact, mixels are characterised by digital numbers corresponding to none of the themes to be classified or have the same values as those of pure pixels belonging to other themes. Clusters of digital values of units are determined either from field reflectance measurements, or from zones identified in the image as uniquely belonging to one of the units under consideration. The dividing line is represented in this example as corresponding to a composition equal to 50% of each of the two pure units.
