Finding Moving Evaders in Terrains Using a Chain of Seekers

In this paper, we propose algorithms for computing optimal trajectories of a group of flying observers (such as helicopters or UAVs) searching for a lost child in a hilly terrain. Very few assumptions are made about the speed or direction of the child’s motion and whether it might (either deliberately or accidentally) try to avoid begin found. This framework can also be applied to a set of seekers searching for hostile evaders such as smugglers/criminals, or friendly evaders such as lost hikers. We show how to plan trajectories (locations and velocities) of each of the seekers so as to maximize the probability that the child is found, while coordinating the motion of the seekers to include constraints based on: visibility region of the seekers, determined by line of sight limitations due to terrain features; and operational time of seekers. Our algorithm explores useful I/O-efficient data structures and branch-cutting techniques to achieve further speedup in execution time by limiting the storage requirements and total number of graph nodes searched, respectively.