In land management, conflicts are more frequent and stronger. Any important project on land becomes difficult to implement. MAGISTER (Multicriteria Analysis with GIS for TERritory) model proposes a decision support method to integrate multiple actors of land management. It is based on geographical information systems and multicriteria analysis. In land use problems, the study area is described by a set of homogeneous zones to reduce the numbers of alternatives. The homogeneity quality is assessed by use of a valued closeness relation developed in the domain of rough set theory. This function is based on the same principle as the valued outranking relation used in ELECTRE, which is then used to select the best zones, or classify them in predefined category. One application of the MAGISTER model concerns the realisation of a land suitability map for housing. Through eight criteria, this map integrates simultaneously the particularity of each place and the general principles of land management, which should be determined by decision-makers.