To create a compliant copy of boats that have been sunk for centuries, Avena relies on a FARO arm with built-in 3D scanner to measure the original parts, which often have complex shapes.
Archaeological research on sunken ships often provides valuable lessons about the ships themselves but also about the historical context. This is the case of the wreck Aber Wrac'h 1 discovered in 1985 in Finistère, Brittany. The evidence and architectural details quickly made it possible to date the ship (between the end of the 14th and the beginning of the 15th century) and to know that it was probably transporting goods between France and Spain. But the researchers wanted to know more because the ship differs from the medieval ships discovered until then, both in its elongated shapes and in its dimensions (it is 26 m long and 7 wide). "In our research, we attach great importance to the precise reconstruction of the boat. This involves making measurements of the sunken parts," explains Alexandra Grille, an underwater archaeologist, who devoted a thesis on this discovery to the Lamop laboratory at the University of Paris 1. Research continues today within a broader framework within the Avena organization.
Photos taken from various angles, including using photogrammetry techniques, had made it possible to make a first digital representation of the boat. "We wanted to go further in rebuilding and rely on 3D measurements made directly on the original parts," continues Alexandra Grille. Avena obtains administrative permissions to remove the parts from the water for a limited time, time to do examinations and checks.
Carpenters of yesteryear worked with axes, respecting the shape of trunks and branches, so that the frame parts have complex geometries. To measure them in 3D, with correct accuracy and in record time, Avena knew that FARO's measurement stocking has become a standard in underwater archaeological research. It was used by researchers at Trinity St. David University in Wales, with whom Avena has had a close relationship since the discovery in 2002 of the Newport, a vessel with many similarities to the Aber Wrac'h 1. For its new excavation campaign, Avena used a FARO Edge ScanArm measuring arm. Welshman Toby Jones provided control, building on his experience on the Newport (of which 2000 pieces were checked). In two weeks, some thirty pieces selected for their interest were reassembled to be checked, and immediately put back into the water. The dimensions range from 20-25 cm for the smallest, to 2.3 m for the larger ones.
In this case, accuracy is not a problem. The difficulty is to make exhaustive measurements for a fairly short period of time, without the possibility of returning to the part (since it has been put back into the water). "With the FARO arm, these complicated things are simply done. Some landmarks (stainless steel screws) are placed on the control parts, so that the measurements taken are not questioned, even if the part is moved during the inspection.
Recording the measurements and transferring them immediately to our 3D reconstruction software is also an invaluable contribution," argues Alexandra Grille. The software in question is Rhinoceros de McNeel. Like FARO's arm, it has become a standard in underwater archaeology. The two make the pair and there is even a very active community (on Facebook) bearing the name FARO Rhino Archaeological User Group (FRAUG)!
The Association for the Study and Valuation of Ancient Wrecks and Ships (Avena) is a structure in which we find various specialists in underwater archaeology. Avena seeks to reconstruct the history of sunken ships, their country of origin, the construction techniques implemented, the ship's vocation, its navigational areas and the causes of the sinking. It was created to study the wreck Aber Wrac'h 1, which is a major discovery for the study of the navy in medieval times.
Find out more: https://www.faro.com/fr-fr/produits/metrologie/bras-de-mesure-faro-scanarm/apercu