This contribution presents the methodology of data acquisition concerning human activities in the Bay of Brest (Brittany, France). The objective is to model potential conflicts and potential impacts on renewable resources. A survey method was developed to collect spatial data from stakeholders using GIS as a mediation tool. Thirty-nine semi-structured interviews were carried out with key informants about several activities. A tablet PC enabled them to map their practice areas on a touch screen. These areas complement a multi-layer GIS database and provide maps for organised activities such as commercial fishing, nautical sports (windsurfing, sailing, kayak, rowing, scuba-diving) and maritime transportation (passengers). The use of GIS, and especially its dynamic multi-scale display capacity, also gives us the opportunity to monitor geographic data layers and scales used by stakeholders while disclosing their practice areas. This integrated GIS based methodology allows us to formalise the stakeholders experience and knowledge. Its contribution to a participatory process such as the Integrated Coastal Zone Management is discussed.