To create an exact copy of the ships sunk centuries ago, Avena relies on a FARO arm with integrated 3D scanner to measure the often complex original parts.
Archaeological research on sunken ships often provides valuable information about the vessels themselves, but also about their historical context. Such is the case of the Aber Wrac'h 1 wreck discovered in 1985 in Finistère, Brittany. The elements removed and the architectural details quickly made it possible to date the ship (between the end of the 14th and the beginning of the 15th centuries) and to determine that it was probably used to transport goods between France and Spain. But the researchers wanted to know more, as the ship stands out from other medieval vessels discovered to date, both in terms of its elongated shape and its dimensions (it is 26 m long and 7 m wide). "In our research, we attach great importance to the precise reconstruction of the ship. This involves measuring the sunken parts," explains Alexandra Grille, an underwater archaeologist who wrote her thesis on this discovery at the Lamop laboratory of the University of Paris 1. The research is now being pursued within a broader framework by the Avena organization.
Photos taken from various angles, using photogrammetry techniques in particular, had enabled us to produce an initial digital representation of the boat. "We wanted to take the reconstruction a step further, and rely on 3D measurements taken directly on the original parts," continues Alexandra Grille. Avena obtained the administrative authorizations to take the parts out of the water for a limited time, to allow time for examinations and controls.
The carpenters of yesteryear worked with an axe, respecting the shape of trunks and branches, so that structural parts have complex geometries. To measure them in 3D, with the right precision and in record time, Avena knew that FARO's measuring stocking had become a standard in underwater archaeological research. In particular, it was used by researchers at Trinity St David's 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. Welshman Toby Jones was in charge of the controls, drawing on his experience gained on the Newport (2000 parts of which were checked). Over a two-week period, some thirty pieces selected for their interest were brought up for inspection, and immediately returned to the water. Dimensions ranged from 20-25 cm for the smallest, to 2.3 m for the largest.
In this case, precision is not a problem. The difficulty lies in carrying out exhaustive measurements over a fairly short period of time, without the possibility of returning to the part (since it has been returned to the water). "With the FARO arm, these complicated things are easy to do. A few reference points (stainless steel screws) are placed on the parts to be inspected, so that the measurements taken are not called into question, even if the part is moved during the inspection.
Recording measurements and transferring them immediately to our 3D reconstruction software is also invaluable," argues Alexandra Grille. The software in question is McNeel's Rhinoceros. Like the FARO arm, it has become a standard in underwater archaeology. The two go hand in hand, and there's even a very active community (on Facebook) under the name FARO Rhino Archaeological User Group (FRAUG)!
About AVENA
The Association pour l'Etude et la Valorisation des Epaves et Navires Anciens (Avena) is a structure that brings together various specialists in underwater archaeology. Avena seeks to reconstruct the history of sunken ships, their country of origin, the construction techniques used, the purpose of the vessel, its navigation areas and the causes of sinking. It was set up to study the Aber Wrac'h 1 wreck, a major discovery in the study of medieval shipping.
Learn more: https://www.faro.com/fr-fr/produits/metrologie/bras-de-mesure-faro-scanarm/apercu