Underwater Ranging and Localization

This chapter focuses on two localization schemes that are developed and evaluated using OFDM modem prototypes. Both approaches are based on range measurements, and are applicable to a network with multiple nodes. The chapter presents the localization approach based on messages broadcast from multiple surface nodes, coupled with tracking algorithms and implemented on a physical system to provide a complete analysis. The advantage of the proposed localization method is that the broadcast messages can serve an arbitrary number of underwater nodes once they are in range, in contrast to many existing solutions which can only serve a small number of users. An on‐demand asynchronous localization (ODAL) scheme is presented. Several fixed‐position anchor nodes are deployed throughout the network and are assumed to have perfect knowledge of their own positions. These anchors need only know their own locations, and are not required to be surface nodes or have synchronized clocks.