  Coverage is one of the fundamental issues in wireless sensor networks (WSNs).
It reflects the ability of WSNs to detect the fields of interest. In a real
sensor networks application, the detection area is always non-ideal and the
terrain of the detection area is often more complex in applications of
three-dimensional sensor networks. Consequently, many of the existing coverage
strategies cannot be directly applied to three-dimensional spaces. This paper
presents a new coverage strategy for the three-dimensional sensor networks.
Sensor nodes are uniformly distributed. The cost factor is utilized to
construct the perceived probability and the classical watershed algorithm after
the transformation of points from the three-dimensional space to the
two-dimensional plane using the dimensionality reduction method, which can
maintain the topology characteristic of the non-linear terrain. The detection
probability in the optimal breath path is used as the measure to evaluate the
coverage. Simulation results indicate that the proposed strategy can determine
the coverage with fewer nodes, while achieving the coverage requirements of the
networks.
