Accurate Geo-Referencing Method for AUVs for Oceanographic Sampling

The objective of the paper is to understand, characterize and enhance the achievable performance of the system of a state-of-the-art marine observation device, the Oceanserver IVER2 Autonomous Underwater Vehicle( AUV), in the Singapore coastal zone and with regard to accurate sampling of oceanographic properties. This paper discusses modifications made to the AUV, in order to make it useful for experiments in this region, which includes shallow water, strong currents, poor visibility, heavy traffic and a poor acoustic environment. These factors strongly influence the choice of navigation method and the system architecture which will enable the AUV to obtain accurate geo-referenced oceanographic properties, and to ensure its safe operation. Our science experiments usually involve sampling at various areas around the coast of Singapore within the same day; this calls for consistent positioning methods that allow ease in deploying and retrieving related equipment. This paper illustrates the use of ultra-short baseline (USBL) tracking system and ranges from an acoustic modem fused by a particle filter to aid the dead reckoning algorithm of the IVER2. The performance of the modified system is shown through simulations and field experiments.