Defining Polycentric Urban Areas Through Commuting Cohesion in France - Methods for Multilevel Analysis and Visualisation of Geographical Networks - page 198

Fig. 12.17 Scale free
structure of (star topology)
and the structure of the dense
sub-graph (zone colored blue
by applying the strength -
density cohesion zone) (color
figure online)
Fig. 12.18 Level of density
cohesion zone - image of a
polycentric event
of these phenomena. By filtering the data based on a gravity model in the first stage,
we visualize the graph based on an accepted definition of polycentrism. Through
metrics applied to the examples around Lyon, Marseille, Lille, Toulouse and
Bordeaux, we then analyze the topological structure of the graph. The betweenness
centrality allows us to locate the major French cities. Their power to attract workers
from the surrounding municipalities is seen through the network growth around
them. The strength index highlights the polycentric structure of the urban areas.
In the examples of Marseille and Lyon, which evolve over time, the polycentric
structure not only develops through the creation of new subcenters, but also through