This paper presents a research experiment that started in 2007 on the French "blue and green infrastructures". At the prompting of a French local administration, this experiment takes into account ecological stakes and involves actors in territorial planning at a metropolitan scale. Founded on previous works, the goal of the approach builds a participative workshop based on GIS and MCA coupling in order to think collectively and better understand the initial foundation of the method, the problems and proposed solutions, and the theoretical and the practical prerequisites. The final goal suggests methodological solutions to facilitate its generalization and its diffusion. The objectives are: 1) to analyse as objectively as possible the initial approach, methodological and technical choices, constraints, limits, and potential improvements; 2) to take into account questioning about the participative workshop conception and functioning; 3) to test new methodological proposals.