Remarks and Errata

Some readers have requested clarification about the assumptions on the capabilities of searchlights. In particular, about whether boundary searchlights can rotate past their adjacent walls. As stated in the literature, a searchlight is a rotatable beam sensor which ``cannot penetrate the environment boundary''. It is intended here that the environment boundary only restricts a searchlight's ability to sense, not its rotation. All searchlights, even those located on the environment boundary, are free to rotate 360 degrees. A beam may thus have length zero if its respective searchlight is aiming into a wall, but it is free to aim there. This assumption on searchlight rotation capabilities is the most natural because it means that there is no discontinuity in a searchlight's rotation range as its location approaches and then goes onto the environment boundary. There also are important computational implications of the assumption, e.g., to guarantee a rotation monotone schedule exists as in Conjecture 3.1 of the IJCGA paper A Complete Algorithm for Searchlight Scheduling (Chapter 3, Conjecture 3.1 of the dissertation Visibility Problems for Sensor Networks and Unmanned Air Vehicles).

In the GNC paper Sampling-Based Roadmap Methods for a Visual Reconnaissance UAV and Chapter 5.3 of the PhD dissertation Visibility Problems for Sensor Networks and Unmanned Air Vehicles, the convergence theorems require a general position assumption. We provide a detailed description of the general position assumption in Section IV.A of this JGCD article.

Last modified: Sun Feb 5 23:07:27 MST 2012