**4. Standardization of appreciation criteria**

MCE requires that the values contained in the different criterion map layers be transformed to similar units [11]. A number of approaches can be used to make criterion map layers comparable. The fuzzy membership approach is one of the standardization methods that have been proposed [10]. For this reason, fuzzy sets were used in this study. To apply fuzzy functions in the GIS environment in this case study, all the map layers are transformed to a raster format with 100 m pixel size. Four fuzzy set membership functions are provided in IDRISI: Sigmoidal, J-Shaped, Linear and User-defined. Our choice has been made relying on two types of factors (environmental and socio-economic) that have been standardized in one common interval from ranging from 0 to 10.
