Fig. 6From: Geographical model-derived grid-based directional routing for massively dense WSNsRouting direction and routing paths. Here, the sinks indicated by circles are located at and , and the black regions represent the holes. a Routing direction \(\widetilde {\mathbf {u_{f}}}\). b Routing paths: the source is close to the grid point . c Routing paths: the source is close to the grid point Back to article page