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Deep-Ocean Services
The side-scan sonar towfish is launched from Odyssey's search vessel
The side-scan sonar towfish uses sound waves to image the ocean floor
The side-scan sonar image of the SS Republic shipwreck site
Promising shipwreck targets are inspected by the ROV
A recovered artifact may aid in further identification of a shipwreck site

Search

Searching for lost ships in the modern day requires enormous skill, patience and specialized technology.

Odyssey's shipwreck search operations are conducted from a research vessel fitted with survey equipment and a Remotely Operated Vehicle (ROV). Using cutting-edge side-scan sonar and magnetometers, Odyssey's ships can comb seemingly endless hostile seas 24 hours a day, seven days a week.

A search typically begins with a side-scan sonar survey of the target area, which is typically paired with a magnetometer survey. The most interesting anomalies on the ocean floor are then inspected visually with an ROV, which sends real-time video images to monitors on the survey vessel for observation by the scientific and technical teams. These images are also downloaded and saved for additional evaluation ashore.

Sometimes, it is immediately obvious whether the inspected site is of interest or not - as in the case of geology, modern debris or when coins or valuables are readily apparent on the site. In other instances it may take many hours of research and return visits to a site to arrive at probable or positive identity and to determine the next step forward.

 

More detailed information about Odyssey's search operations

Side-scan sonar serves as a cross between radar and aerial photography, a highly effective geophysical remote sensing tool. Transducers housed in a side-scan sonar towfish are towed behind the research vessel at varying meters above the seabed depending on the range and resolution desired at the time. This is typically between 20-50 meters above the seafloor. When targets of interest are identified and further side-scan surveyed, the 'fish' is towed as close to the target as possible. This is typically between 7-15 meters above the seafloor.

Pulses of sound energy are bounced onto the seabed in a fan-shaped arc. In fractions of a second the return echo is processed as a sonar image exposing anything protruding above the seabed as small as a pipe, oil drum or a cannon. Hard objects like metal provide the strongest echo, yet pottery, rock and other relatively hard objects will also reflect well. Materials that are less dense such as a degraded wooden ship’s hull, provide a weaker echo. When the echo from the object on the ocean floor is received, it is converted into a side-scan sonar image depicting the object’s shape, form and shadow.

These reflected acoustic returns create an image similar to an aerial photograph which can be viewed live on a computer monitor on the research ship. Under optimum conditions, this sonogram can be as detailed as a photograph. In other circumstances, side-scan sonar images of wrecks of international historical importance can look like nothing more than a pin prick-sized smudge on the seabed, offering no indication of its true character.

To maximize the interpretative capabilities of non-disturbance remote geophysical sensing, Odyssey also uses magnetometers which identify targets with high magnetic signatures standing out from the background values of the seabed. The magnetometer can be towed above the seabed at the same time the sonar survey is carried out.

Every anomaly on the ocean floor is recorded and then analyzed by Odyssey's team of specialists. The most promising anomalies (based on size, shape, location, our past experience and other factors) are then considered potential targets. These are then visually inspected using an ROV, which is configured with high-definition video and still cameras and additional navigation cameras designed to help direct the ROV pilot as he maneuvers to get a closer look at the site. The ROV is operated from the research vessel stationed on the surface of the ocean. Live, high-definition video images of the seabed targets are sent back to the control room of the research vessel for review and analysis. In some instances, an artifact will be recovered by the ROV to assist in the potential identification or dating of a site.

Because a side-scan sonar survey has to cover enormous stretches of seabed, the remote sensing surveys are pre-planned and plotted using GPS to follow meticulously designed search grids. At times, bathymetric surveys are conducted prior to side-scan operations or during the archaeological survey of a site.

Odyssey’s survey operations have mapped more than 17,000 square miles of seabed and spent more than 10,000 hours diving on shipwreck sites with a ROV. Nearly 300 shipwrecks have been discovered ranging from third-century BC Punic vessels to modern fishing boats.

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