The problem of a polygonal object moving in an uncertain polygonal environment, i.e. the positions and orientations of the objects relative to each other are not exactly known, is addressed. Furthermore, the moving object does not move exactly as it is commanded to move. Due to these uncertainties, even a motion generated by a correct motion planner may fail, i.e. for instance, an unexpected contact may occur. A situation analyzer that enables the moving object to acquire information on a contact situation is presented. This analyzer uses the nominal world model including information on the magnitude of the uncertainties in order to get hypotheses on the geometric entities involved in the contact. The discrimination among the hypotheses is based on test motions, i.e. motions whose feasibility depends on the validity of a certain subset of the hypotheses.>