Performance of an enhanced passive sonar reflector SonarBell: A practical technology for underwater positioning

Commercial marine activity has driven the need for technological solutions for the positioning and relocation of equipment on the seabed. Traditional solutions often involve localisation through range measurements to several transmitters, but these active devices contain batteries that require periodic maintenance. For this reason, the use of passive sonar reflectors as navigation and localisation aids is desirable. Fundamental to their practicality is their ability to reflect sonar energy, quantified as target strength. Recent advances in commercial passive reflector technology, as embodied by the SonarBell, have made them a practical technology for underwater positioning. In the present work, the acoustic characteristics of passive sonar reflectors and the SonarBell are introduced. The results of basic sonar equation analysis and target strength from broadband calibration measurements in a water tank estimate the performance that could be achieved using SonarBell within localisation systems. Accounts of two in-field tests demonstrate SonarBell being used practically.