Shipwrecks in 3D: underwater archaeologists from Ca’ Foscari tested technological revolution

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Technology is transforming archaeological techniques on land and underwater. For several years now underwater archaeologists have been using special software to transform the pictures taken underwater in detailed three-dimensional models. With this new application of a known technique, photogrammetric processing, maritime excavations become faster, safer and cheaper.

How does it affect the quality of the findings? What measures should the researcher take to make the most of the investigations? In a research published in the Journal of Cultural Heritage and mentioned by Science the maritime archaeologist and professor at the Department of Humanities at Ca’ Foscari Carlo Beltrame dealt with these questions with his team, thanks to a collaboration with the photogrammetric lab at IUAV University.  

The key instrument is the camera, to take hundreds of pictures from many different angles of underwater excavations, associated with a precise topographic net on the site.

“With photogrammetric we save many working days underwater - Beltrame explained - and in just a few hours we can create a detailed three-dimensional model of the excavation in our computer, and calculate volumes with an irrelevant margin of error. It is a genuine revolution”.

The team tested photogrammetric on different sites with different depth and environmental conditions. Darkness or the dissolving of colors linked to depth, or high turbidity water were identified as troubling for photography as well as the extension and complexity of sites and the short periods of stay linked to the increase of depth.

Antiquity finds can be found all over the Mediterranean seabed and three-dimensional reconstructions facilitate to imagine how ships were like, how much material they were carrying, how it wrecked. The excavations include “the routes of marble” project (ITALIAN) and the shipwreck of Cape Stoba (ITALIAN) loaded with wine amphoras that sunk a thousand years ago in Croatia (see the video reconstruction).

In the last mission carried out in the Summer of 2017 the underwater archaeologists from Ca’ Foscari went to Capo Taormina. The site was documented for the first time in 1959 by Gerhard Kapitaen. It consists of 33 fragments of columns on a rocky seabed at 21-26 meters deep. This investigation was possible thanks to a collaboration with the Sea Superintendence in Palermo, the firm Idra in Venice and Diving Taormina.

It was also possible thanks to the grant of the Honor Frost Foundation that supported the design of a 3D photogrammetric model and to conduct sampling. Its analysis is still carried out at the LAMA lab at IUAV University; it recognized the marble as green African marble from Teos (in modern Turkey).

The overall weight of the cargo, about 100 tons, is the smallest documented by the team and a bronze element of carpentry which is the only remain of the ship suggests that the ship was 20 meters long and sunk hitting the rocks of Capo Taormina between the end of the 2nd and the end of the 4th century. This and other 3D models will be used to create virtual reconstructions of antique ships.

Where will the routes of marble and these technological innovation bring the researchers? “The final frontier yet to be explored in the application of photogrammetric is deep sea - says Beltrame - and we are currently designing a project on shipwrecks at more than 100m deep, for which we will need deep sea divers or even underwater ‘drones’”.