Deep-water Archaeological AUV Surveys and Photo Capabilities

Abstract

Abstract In January 2001, C & C Technologies, Inc. placed into full operation the first commercial deep-water Autonomous Underwater Vehicle (AUV) in the Gulf of Mexico. The application of this advanced technology was immediately beneficial to the survey industry as well as having a profound impact on deep-water archaeology. Over twenty-four shipwrecks and several additional potential wrecks have been discovered and/or investigated using C & C's AUVs. Several of those surveys resulted in new discoveries and at least, thirteen of the wrecks have been confirmed to be historic vessels. The initial primary geophysical instrument payload of the HUGIN model AUV consisted of dual frequency side scan sonar, subbottom profiler, and multibeam bathymetry. In 2009, C & C added a digital still camera to the vehicle allowing relatively quick visual confirmation of seafloor targets. The photos and photo mosaics produced from the camera surveys have further advanced deep-water archaeological investigation and mapping. This paper focuses on the archaeological application of the AUVs and in particular the photographic capabilities and utilization of those photographs. Introduction Autonomous Underwater Vehicles (AUVs) are built for a variety of purposes and come in many shapes and sizes with near limitless combinations of sensors and payloads. Camera systems are a relatively new addition to some of the deeper AUV systems. Currently, there are only a few companies, institutions, or government agencies (e.g. C & C Technologies Inc. (C & C), Kongsberg, Woods Hole Oceanographic Institution (WHOI), the United States Navy, etc.) that operate AUVs equipped with digital still cameras capable of survey to 1,000 meters or deeper. This paper will focus primarily on the C-Surveyor AUVs, which are HUGIN 1,000, 3,000, and 4,500 meter systems (Figure 1). All references to " AUV?? in this paper refer to one of the C-Surveyor AUVs unless otherwise specifically stated. Four AUVs have been added to C & C's fleet over the last decade as well as several payload and sensor upgrades. Although the sensor payload of each AUV may be slightly different, the basic payloads include an EM 2000 multibeam bathymetry system (Figure 2), Chip Edgtech subbottom profiler system (Figure 3), and duel frequency side scan sonar at 410 kHz and either a standard 120 kHz frequency or a 230 kHz dynamically focused sonar system (Figure 4). Three of C & C's AUVs (the 3,000 and 4,500 meter systems) are equipped with digital still cameras (George 2009a). The navigation/positioning system for the AUVs utilize a Kalman filter algorithm, which uses input data from a Simrad High Precision Acoustic Positioning (HiPAP) System, inertial navigation, and Doppler velocity speed log. The post-processed positions for the AUV are accurate to within ± 5 meters at a depth of 3,000 meters.