Robots and drones have recently become commonplace, with more advanced and affordable units available every year. While initially they may have been marketed primarily to hobbyists, consumer robots (and drones in particular) have become much more than just toys; they have garnered more and more attention from researchers across fields such as environmental sensing, surveillance, computer vision, machine learning, systems engineering, and networking. Robots and drones provide a rich playground in which to tackle challenging problems aimed at increasing the autonomy of machines. Moreover, as these machines become ever more ubiquitous, there arises both the desire and need to provide a way for them to coordinate their movements and actions so that they can accomplish tasks such as navigating without collision or mapping an area. Such coordination becomes more difficult once the space that must be navigated is in a GPS-denied area. In this chapter, the many facets of robot and drone coordination in GPS-denied areas are discussed, addressing issues associated with localization and coordinating multiple agents as they attempt to accomplish a common goal.
