Archaeological Excavation and Recovery
Odyssey's archaeological excavation and recovery operations combine high-tech robotics including Remotely Operated Vehicles (ROVs) with sophisticated positioning systems, cameras and specialized computer hardware and software to carefully record the location of artifacts in situ and to document the entire archaeological process as the artifacts are recovered from a shipwreck site. As they conduct robotic archaeological operations at sites hundreds -and sometimes thousands -of feet below the ocean surface, Odyssey's ROV pilots are directed by marine archaeologists aboard the recovery vessel.
The Odyssey Explorer, a 251-foot Class II dynamically positioned (DP) ship, serves as Odyssey's principal state-of-the-art deep-ocean archaeological platform. She carries fuel and stores for missions of up to 60 days, accommodates 42 crew, including technicians, scientists and archaeologists, and has extensive onboard storage space for workshops, an archaeology laboratory, multiple cranes and a large A-frame for exceptional handling capability. When working on a project, operations are generally conducted 24 hours a day, seven days a week.
The centerpiece of Odyssey's advanced robotic archaeology system is a Remotely Operated Vehicle (ROV) which serves as the archaeologist's eyes and hands in the deep ocean. Odyssey owns two work-class ROVs, nicknamed ZEUS and ZEUS II. The 200 HP and 400 HP vehicles respectively, are each approximately the size of a small truck; they stand about 10 feet high and weigh eight tons. Driven by eight powerful hydraulic thrusters, they are rated to operate up to depths of 2,500 meters (8,200 ft). Both ROVs have been custom-designed for deep-ocean archaeological survey and recovery operations, including visual inspection, pre-disturbance photographic and video documentation, scientific excavation and artifact recovery. As ZEUS and ZEUS II are nearly identical, and can be used interchangeably, all references to ZEUS below also apply to ZEUS II unless otherwise noted.
ZEUS is equipped with advanced acoustic positioning gear and telemetry, as well as a suite of HMI lights to illuminate pitch-black wreck sites and to enable high-definition still and video cameras to transmit images live from the seabed. ZEUS is remotely piloted by two technicians manipulating joysticks from the recovery ship on the surface above the wreck site. One pilot "flies" ZEUS while the other operates the manipulator arms. These pilots receive instructions from the archaeologist who oversees the entire operation and directs the excavation methodology, including ZEUS’ movements on the seabed. Both archaeologist and pilot watch the same live high-definition video feed on TV monitors aboard the recovery ship.
The two manipulator arms on ZEUS are capable of lifting objects comparable to the weight of an average man. Small and delicate artifacts are picked up individually with a silicone or rubber limpet suction device attached to the ROV’s port manipulator arm.
Integrated into ZEUS is Odyssey's proprietary Sediment Removal and Filtration System or SeRF™ for short. This venturi system channels sediments and small artifacts into a collection and filtration chamber to capture very small artifacts, such as buttons, fragments, or seeds, while sediments exhaust through an opening at the rear of the container. The SeRF™ unit may also be configured to retain sediments for sieving. The system has been employed to clear and excavate sections of wreck sites that the archaeologist wishes to examine for the presence of artifacts and ship structures. The venturi system can also be reversed to “dust off,” and gently clean the surface of the site to expose artifacts and structural elements without disturbing the main matrix.
Odyssey has developed an extensive digital archive using its unique data logging system to record all events and activities. Known as DataLog™, it receives and processes data from the ROV in real time. All activities, observations and artifact manipulations are logged through drop-down menus and accompanied by a comment typed by the operators aboard ship. The system is manned around the clock, 24 hours a day when the ROV is in the water. The program automatically logs all events, including time, date, dive number and X, Y, Z coordinates of the ROV's position and of each artifact recovered. Every second of every dive is recorded on high-capacity digital video disk (DVD) in triplicate. Archaeological and other interesting footage is recorded on DVD and high definition videotape and, where required, still photographs are produced and logged. Additionally, a complete video and photo record is created and preserved indefinitely. These logs allow complete reconstructions and post-dive analysis of each dive event. Data sheets, maps and reports essential for a variety of projects can then be created from this comprehensive digital archive.
While Odyssey may recover a small number of artifacts to file an admiralty arrest of a site or to assist in the identification of a shipwreck, before any excavation begins an archaeological pre-disturbance survey is conducted which includes a high-resolution photomosaic and production of a site plan.
The photomosaic is comprised of thousands of high-resolution images that capture and document the entire wreck site. To create the photomosaic, still cameras mounted on Odyssey's ROV take continuous, overlapping photos of the site. Photo technicians aboard the ship then digitally "stitch" the images together—a painstaking process. The photomosaic serves as an invaluable tool for understanding the archaeology of the site, for developing a visual base for a master site plan, and for planning the archaeologist's excavation strategies. It also provides a permanent record of the shipwreck site for future study.
Within this pre-disturbance observation phase, Odyssey also records all exposed archaeological features (cannon, anchors, concretions, pottery and other artifacts, brick, wooden hull structure, and other visible items), as well as the abundant garbage often scattered across a wreck site. The image of deep-water shipwrecks lying in pristine time capsules is regrettably one of the great myths of marine archaeology.
Further, in collaboration with world experts and scientists, Odyssey examines shipwreck environments, the sediments, biological growth and marine species attracted to wreck mounds as artificial reefs and living habitats.
Once the photomosaic is complete, the archaeological excavation and recovery of artifacts may begin. First, before excavations start, acoustic transponders are planted on the seabed around the perimeter of the wreck site. Acoustic signals transmitted from the transponders and traveling at a known speed then measure the distance between each transponder and the ROV, which triangulates into a position for the ROV.
A grid of 1 x 1 square meters is then electronically generated across the wreck’s horizontal surface so that every artifact can be recorded within its unique context – precisely as artifacts are recorded on terrestrial and shallow water sites. The difference, however, is that on Odyssey projects measurements are taken acoustically by bouncing sound waves between the wreck, transponders and datum points, and not by hand using pen and paper. ZEUS' manipulator arms are equipped with special technology that allows the exact x,y and z coordinates of every artifact touched or recovered to be recorded in the electronic DataLog™ database.
Sediment may be excavated using a six-inch diameter Venturi hose (part of Odyssey's SeRF™ system) which can blow or vacuum sand very slowly and lightly or with more speed and pressure. Sediment can be filtered into compartmentalized baskets attached to the back of the ROV ZEUS. Once a dive is completed, the spoil is sieved on land for small finds and environmental data (seeds, wood, snails and other items).
When delicate objects need to be recovered, a soft silicone or rubber limpet attached to ZEUS’ port manipulator arm is used. This suction limpet uses changeable pressure to pick up wood, coins, glassware and other fragile finds. Throughout this process every step is controlled and monitored by an archaeologist, who also ensures every phase of a dive is logged in Odyssey’s customized data software. Video footage and still photography further document the context of each object in relation to other objects, as well as preserved ship structure and the seabed environment.
As each individual artifact is carefully lifted and placed in a numbered recovery basket, its position is systematically documented by data-loggers who track all activities performed by the ROV during each dive to the wreck site. The recovery baskets or individual artifacts are sealed and protected in closable miniplex units for their voyage to the surface vessel.
When this recovery container is lifted to the surface, it is transported to the nearby conservation deck on the Odyssey Explorer. Here the archaeologists and skilled assistants carefully begin detailed recording, photography and documentation of each object, followed by on board "first-aid" conservation whereby the artifacts are stabilized and placed in environmentally-controlled storage until they are transported to Odyssey's land-based conservation facility.
Once on land, all artifacts from a porthole to a button can be precisely tracked back to their original resting spots (archaeological contexts) on any shipwreck.
The highly complex logistics demanded by deep-water excavation rely on close teamwork bringing together highly skilled and dedicated archaeologists, ROV pilots, data loggers, conservators and project managers. During the SS Republic archaeological excavation, ZEUS completed 262 dives on the wreck site and logged almost 3,500 hours on the site – every minute recorded by high-resolution video on DVDs and tape. The ROV’s longest uninterrupted dive lasted 72.5 hours. A database with over 60,000 records was created by the underwater research team and more than 13,000 digital still photographs were taken during the entire operation.
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