1 Introduction
Intensive research activities have been dedicated to autonomous vehicles, such as unmanned aerial vehicles (UAVs), autonomous surface vehicles (ASVs), and unmanned ground vehicles (UGVs). Pertinent technologies include indoor localization (see [1], [2], [3], [4]), range-free localization (see [5], [6], [7], [8], [9]), and path-tracking (see [10], [11], [12], [13]). Localization using mobile sensors enables mobile devices to pinpoint other devices with high accuracy. Another interesting topic is the tracking (scouting) strategy, which has been crucial for home robots such as autonomous lawn-mowers, autonomous house-keepers, etc. The basic tracking strategy contains three major aspects: routing, patrolling, and navigation.