Gridding the site

In order to locate the ship's remains spatially, researchers initially decided to use a flexible grid system, consisting of polypropylene halyards stretched between steel reinforcement bars. Each square in the grid measured 3 x 3 metres. The x-axis of the grid was assigned letters, while the y-axis was numbered.
In 2003, due to the currents and the intertwined and uneven topography and structures of the wrecks, the team switched to a rigid grid. It had a modular, adjustable-height framework that was easy to install. It was resistant to both currents and the weight of seaweed, and allowed researchers to create architectural cross-sections and measure the wrecks' elevations. This framework, made of aluminium and stainless steel, was inspired by a model that had been used for many years by underwater archaeologists working for Parks Canada, a Canadian government organisation. However, it differed from its predecessor in several respects, including the size of its squares (3 x 3m, instead of 2 x 2m) and its extra sturdiness in order to resist the exceptionally strong currents. It was manufactured at Saint-Malo in the spring of 2003 by Atelier Polyvalent Plaisance, and was fitted with measurement tapes attached to its horizontal elements and removable feet.

Multimedia

: Teddy Seguin (Adramar) © MCC / DRASSM
: Rigid grid placed over the wreck of the Dauphine. An iron cannon is visible in the foreground. (Réf. : NAT05_SM0336)

: Frédéric Osada (Images Explorations) © MCC / DRASSM
: Up until 2002, a flexible grid was used for the excavation of the site. (Réf. : Nat02_SM0697)

: Elisabeth Veyrat © MCC / DRASSM
: Sketch included in the specifications for the future rigid grid.

: Teddy Seguin (Adramar) © MCC / DRASSM
: Installation of the rigid grid. (Réf. : Nat05_SM077)

: Teddy Seguin (Adramar) © MCC / DRASSM
: Daily inspection of the height of the gridwork in order to take measurements along the Z axis. (Réf. : Nat05_SM189)

: Taking measurements along the X, Y and Z axes. Detail of one of the horizontal bars of the grid, fitted with a gradated ruler. The ruler, printed on highly resistant vinyl tape, has simplified gradations designed by the excavation team to be read at a distance. They are visible from roughly two metres away.

: Taking measurements along the X, Y and Z axes. The 3 x 3m excavation squares can themselves be subdivided into nine squares, one metre on a side. (Ref. : Nat03_SM0128)

: The variations in level between one part of the site and another sometimes made measuring difficult. (Ref. : Nat05_SM094)

: Grid bar, broken during the winter. At the end of the 2003 campaign, the team decided to leave three 3 x 3m excavation units in place, in order to have a fixed reference point to faciliate reinstallation of the grid in 2004. The frames that were left on site were lowered all the way down, and their feet anchored in the substratum. When the team returned the following year, none of the frames were in place. Their elements – disconnected, bent and broken – were finally located several dozen metres away. They were likely snagged by a dragnet. (Réf. : NAT04_M275)