Return to Antikythera: Multi-session SLAM Based AUV Mapping of a First Century B.C. Wreck Site Stefan B. Williams, Oscar Pizarro and Brendan Foley Abstract This paper describes an expedition to map a first century B.C. ship wreck off the coast of the Greek island of Antikythera using an Autonomous Underwater Vehicle (AUV) equipped with a high-resolution stereo imaging system. The wreck, first discovered in 1900, has yielded a wealth of important historical artefacts from two previous interventions, including the renowned Antikythera mechanism. The deployments described in this paper aimed to map the current state of the wreck site prior to further excavation. Over the course of 10 days of operation, the AUV completed multiple dives over the main wreck site and other nearby targets of inter- est. This paper describes the motivation for returning to the wreck and producing a detailed map, gives an overview of the techniques used for multi-session Simultane- ous Localisation and Mapping (SLAM) to stitch data from two dives into a single, composite map of the site and presents preliminary results of the mapping exercise. 1 Introduction In September 2014 an expedition was mounted to revisit the site of a first century BC shipwreck off the coast of the Greek island of Antikythera. The project began in 2013 with multibeam mapping and diver-based search of the site of the Antikythera shipwreck in preparation for further excavation. The objective of this second phase of the project was to produce a high-resolution, 3D map of the site using the Autonomous Underwater Vehicle (AUV) Sirius operated by the University of Sydney’s Australian S.B. Williams (B ) · O. Pizarro Australian Centre for Field Robotics (ACFR), University of Sydney, Sydney Nsw 2006, Australia e-mail: stefanw@acfr.usyd.edu.au O. Pizarro e-mail: o.pizarro@acfr.usyd.edu.au B. Foley Woods Hole Oceanographic Institution, Woods Hole, MA, USA e-mail: b.foley@whoi.edu © Springer International Publishing Switzerland 2016 D.S. Wettergreen and T.D. Barfoot (eds.), Field and Service Robotics, Springer Tracts in Advanced Robotics 113, DOI 10.1007/978-3-319-27702-8_4 45