Experimental results of an inexpensive short baseline acoustic positioning system for AUV navigation

The Ocean Engineering Department at Florida Atlantic University (FAU) and the Naval Postgraduate have implemented AUV acoustic positioning systems based on the Desert Star Dive Tracker short base line (SBL) system. The motivation for these implementation efforts was to develop a short range, inexpensive, but relatively high precision navigation system for each institution's autonomous underwater vehicles (AUVs). In the NPS case the SBL system is to support navigation of their Phoenix vehicle in mine reconnaissance type missions where the vehicle needs to more precisely locate obstacles and mine like objects. In the FAU case the SBL system is to support guidance of the Ocean Explorer (OEX) vehicle in rendezvous and docking maneuvers. The Dive Tracker SBL can produce supposed positioning accuracies on the order of 6" rms. FAU has build a portable easily deployed collapsible frame for supporting 3 SBL transducers or beacons. The frame is arranged in star that is anchored to the bottom. The baseline between transducers is approximately 20 ft. The OEX carries a transducer and electronics that compute its position relative to the baseline. A docking target placed near the baseline and anchored to the bottom. The location of the target is then determined by manually positioning the AUV transducer at the target and taking SBL fixes, A series of at-sea tests of this system have been conducted. This paper presents results of the at sea tests of this positioning system off the coast of Boca Raton Florida. The analysis will comment on the efficacy of this type of system for guidance of small AUVs in docking maneuvers.