An Improved On-line Strategy for Exploring Unknown Polygons

We present a new, on-line strategy for a mobile robot to explore an unknown simple polygon P, so as to output a so-called watchman route such that every interior point of P is visible from at least one point along the route. The length of the robot's route is guaranteed to be at most 6.7 times that of the shortest watchman route that could be computed off-line. This significantly improves upon the previously known 26.5-competitive strategy. A novelty of our strategy is an on-line implementation of a previously known off-line algorithm that approximates the optimum watchman route to a factor of $$\sqrt{2}$$2. The other is in the way the polygon exploration problem is decomposed into two different types of the subproblems and a new method for analyzing its cost performance.