Comparative analysis of an underwater acoustic relative positioning system using coded signals

Abstract

Positioning systems in underwater environments constitute a relatively new field of research that is gaining increasing interest in recent days. These systems are useful to locate buoys that are monitoring the environment, as well as Remotely Operated Vehicles (ROVs) or Autonomous Underwater Vehicles (AUVs). An acoustic relative positioning system is presented in this work, based solely on pseudorandom coded acoustic signals emitted underwater and detected by matched filtering processes. One of the buoys acts as the master node, emitting its code through a hydrophone, which will be received by the other buoys. These buoys will after reply with their own code, obtaining the round-trip times of flight (RTOF) for each pair of buoys. Once the RTOFs are obtained, the distances between them can be computed knowing the sound speed value, and from them the positions are calculated by means of the Multidimensional Scaling technique (MDS). Different codes are studied, being the performance criteria the average error between the real and estimated distances. This performance is evaluated using a ray-tracing propagation model, which takes into account the transmission loss due to different phenomena, as well as the dynamic effect of wind-generated waves. © 2012 Acoustical Society of America.