  We describe a new approach for dealing with the following central problem in
the self-organization of a geometric sensor network: Given a polygonal region
R, and a large, dense set of sensor nodes that are scattered uniformly at
random in R. There is no central control unit, and nodes can only communicate
locally by wireless radio to all other nodes that are within communication
radius r, without knowing their coordinates or distances to other nodes. The
objective is to develop a simple distributed protocol that allows nodes to
identify themselves as being located near the boundary of R and form connected
pieces of the boundary. We give a comparison of several centrality measures
commonly used in the analysis of social networks and show that restricted
stress centrality is particularly suited for geometric networks; we provide
mathematical as well as experimental evidence for the quality of this measure.
