Boundary Tracking of Continuous Objects Based on Feasible Region Search in Underwater Acoustic Sensor Networks

Boundary tracking of sea continuous objects (e.g., oil spills and radioactive waste) is a challenging task that can be tackled via underwater acoustic sensor networks. Existing methods operate by selecting sensor nodes in the proximity of the boundary, and tend to over- or underestimate the actual boundary of the continuous object. In this article, a boundary tracking algorithm termed feasible region search for continuous objects (FRSCO) is proposed. To determine a feasible region where the actual boundary lies, the proposed method first bounds the continuous object inside a minimum elliptical boundary. Within the minimum boundary ellipse, cell partition is performed through a binary tree structure, from which a set of backbone cells is selected. These roughly localize the feasible region. By constructing and deconstructing convex hulls of nodes in each backbone cell, the feasible region location uncertainty is further narrowed down. Virtual nodes are introduced in the final feasible region to determine the boundary nodes - by applying the principle of maximum entropy. Similar to virtual nodes, the selected boundary nodes do not need to correspond to the actual sensor nodes in the proximity of the boundary. Results from realistic testbed experiments and simulations show that the FRSCO exhibits effective tracking accuracy.