Commuters'graphs and citie's polycentric cohesion

International audienceThe actually urban dynamics lead to some difficulties in the global apprehension of the city. According to commuters weighted graphs between localities, we propose a new approach to understand those dynamics. Working successively on three scales (urban areas perimeters, sub-centres and each locality), the topic of this research is to measure and visualize the cohesion and the fragmentation of urban spaces. We show an empirical approach of French urban system from data of last four censuses (1975-1982-1990-1999)