Sunken settlements but the hard part is finding them

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sunken settlements, but the hard part is finding them. Underwater research used to require divers to find shipwrecks or artefacts, but in the second half of the twentieth century, various types of underwater vehicles were developed, some controlled from a ship on the surface, and some of them autonomous, which means they don t need to be operated by a person. Autonomous underwater vehicles, or AUVs, are used in the oil industry, for instance, to create maps of the seabed before rigs and pipelines are installed. To navigate they use sensors, such as compasses and sonar. Until relatively recently they were very expensive, and so heavy that they had to be launched from a large vessel with a winch. Q33 Q34 But the latest AUVs are much easier to manoeuvre - they can be launched from the shore or a small ship. And they’ re much cheaper, which makes them more accessible to research teams. They re also very sophisticated. They can communicate with each other and, for example, work out the most efficient way to survey a site, or to find particular objects on the seabed. Field tests show the approach can work. For example, in a trial in 2015, three AUVs searched for wrecks at Marzamemi, off the coast of Sicily. The site is the final resting place of an ancient Roman ship, which sank in the sixth century AD while ferrying prefabricated marble Q35 elements for the construction of an early church. The AUVs mapped the area in detail, finding other ships carrying columns of the same material. Creating an internet in the sea for AUVs to communicate is no easy matter. Wifi networks on land use electromagnetic waves, but in waterthese will only travel a few centimetres. Instead, a more complex mix of technologies is required. For short distances, AUVs can share data using light. Q36 while acoustic waves are used to communicate over long distances. But more creative solutions are also being developed, where an AUV working on the seabed offloads data to a second AUV, which then surfaces and beams the data home to the research team using a satellite. There s also a system that enables AUVs to share information from seabed scans, and other data. So if an AUV surveying the seabed finds an intriguing object, it can share the 117
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coordinates of the object - that is, its position - with a nearby AUV that carries superior cameras, and arrange for that AUV to make a closer inspection of the object. Marine archaeologists are excited about the huge potential of these AUVs for their discipline. One site where they’ re going to be deployed is the Gulf of Baratti, off the Italian coast. In 1974, a 2,000-year-old Roman vessel was discovered here, in 18 metres of water. When it sank, it was carrying medical goods, in wooden or tin receptacles. Its cargo gives us insight into the treatments available all those years ago, including tablets that are thought to have been dissolved to form a cleansing liquid for the eves.
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  • The Passage, Alexander Henderson

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