French regions scale has expanded and the State services have to seize this new territory to think about how to support public policies. At the same time, they need to rebuild their organization and create new practices. How can they hold of the new territory, individually and collectively, by taking into account the diversity of knowledge of institutions and agents? The DREAL Grand-Est (Ministry of Ecology, Sustainable Development and Energy's regional direction) and AgroParisTech have adapted a method of territorial analysis in order to respond to this double challenge of dynamic of scale change and transformation of practices. This approach, called the "method of shared territorial diagnosis", aims to mobilize the uses of geographic information during a participatory process of construction-deconstruction of the territorial knowledge that the agents engage at each stage. This paper shows how the experiment highlights the spatial approach as an intermediary to acquire this multi-scale knowledge by agents and focuses on the points of passage to make a more generic method.