From GISs to TIS (Territorial Information System) : the 3D technologies for intelligibility and decision making in metropolitan area planning: the case of Grenoble Alpes Metropole

International audienceFor approximately 10 years –even more– technical departments or partners of the large localauthorities have build their own GIS and urban, economic, demographic, environmental... data bases.This evolution was –and still is– quite efficient for modelling and managing sectional problems or welldefinedprocesses of the urban functioning (traffic, urban networks, waste collection, land registry...).Most of the time, due to the intrinsic complexity of the involved data as well as to the professional andorganisational cultures and habits, no real coordination between these specialized GIS has been ableto be implemented at a metropolitan scale. Problems caused by the urban increasing and spreadingand requirements of sustainable development though call for providing decisional actors with a global,transversal and expressive representation of the metropolitan area as well as planning andenvironmental issues.Working-out a “super-GIS” integrating data of the multiple specialized GIS exploitable for themetropolitan issues does not seem to be a reachable anymore nor even attractive goal for at leastthree reasons :- metropolitan perimeter is by nature blurred and changing,- metropolitan decisional actors are dramatically different in their way for grasping space andterritory,- matters to be integrated and collated are relevant to very disparate scale levels, temporalitiesand figuration modes.Development of 3D visualization performances enhanced by superimposition abilities of any kind ofGIS data and more generally digital objects or images, is to be changing the way to conceive territorialfiguration. Growing popularity and uses of a commercial product as Google Earth is a symptom -butunquestionably also a factor- of the need of drawing the expert data and the real-life space closer.Propose a virtual 3D metropolitan basement as a shared stage is thus a way for both visuallyintegrating heterogeneous data, and for confronting technically, territorially or politically various pointsof view. For these different reasons an increasing number of metropolitan or regional authorities arebecoming involved in such a work.Related questions and issues proceed from various scientific domains : on the one hand of course,computing and geomatic and urban and environmental planning, and on the other handcommunication and semiology as much as mental representation and decision sociology. Territorialdynamic 3D models are thus a tool for better land planning issues intelligibility and decision making,but also a work in progress for practically linking engineery and social sciences.The submitted communication will first propose a state of art of the main questions and issues relatedto the territorial virtual 3D models working-out and use. After a brief show and comment of a fewrevealing examples (*), design and uses of the metropolitan 3D model of the urban area of Grenoble(700.000 inhabitants inside a mountain environment) developed since for years in a territorial planningand managing purpose, will be presented and analyzed