University of Sydney

Divers used a robotic optics system to create a photorealistic reconstruction of Pavlopetri, an ancient trading post off the coast of Greece.

The world's oldest known underwater city lies frozen in time beneath 3 to 13 feet of water off the southern coast of Greece. Since the ocean swallowed it around 1,000 BC, the infrastructure of Pavlopetri has remained eerily intact. Streets snake around more than a dozen buildings, courtyards and tombs built from uncut limestone and eolianite. Archaeological dating indicates that the settlement of perhaps 500 to 2,000 souls has lain in peace this way since the Early Bronze Age in 3,000 BC, although boat anchors occasionally rake through and stir up whirlwinds of debris.

Since its discovery in 1967, archaeologists have learned much about Pavlopetri, located squarely in the birthplace of Western Civilization. Loom weights strewn around the site suggest it once supported a healthy textile industry. Pitharis storage vessels, possibly imported from Crete, indicate it was big in the long-range trading business. But the tops of many of those vessels are barely sticking above the sand. Much of the good stuff, including possible organic materials like wooden tools and even food, has yet to be dug up.

Well, that task just got a lot easier with the help of the Australian Centre for Field Robotics, a department within the University of Sydney. Today, the center snagged top honor in Canon Australia's "Extreme Imaging Contest" for work it had done in making insanely detailed maps of Pavlopetri. These maps are photorealistic, are in 3-D and will be indispensable for excavating the rest of the ancient outpost. Before, archaeologists were using "point-cloud" maps like this one:

From 'City Beneath the Waves' on YouTube

Now, they have at their disposal nifty maps like the one at the top of this post and like this:

Or even this one, which shows the location of graves from the days of Homer:

 

From the 2011 paper (PDF), "Reconstructing Pavlopetri: Mapping the World’s Oldest Submerged Town using Stereo-vision"

The robotics team was able to churn out such brilliant cartography via a deceptively simple technique: They took a stereo-optics system typically used on unmanned deep-sea submersibles and put it into the hands of a diver, who laboriously followed guide wires above the sunken city until it was thoroughly mapped. This method produces much more detail than traditional sonar mapping, as the device they used is finely tuned enough to pick up individual seashells down below.

Also involved with the effort is the University of Nottingham and the Greek government. You can read more about it at the Pavlopetri Underwater Archaeology Project and in the publications of robot-master Stefan Williams, a recipient of the Canon prize.

About the Author

John Metcalfe
John Metcalfe

John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.

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