Underwater Recording - Page 1 of 2

 

A number of different types of recording were used underwater: traditional survey; DSM or Direct Survey Measurement; various types of photography; and drawings, sketches and notes from the archaeologists and volunteer divers.

In l976 and again in 1979, Nigel Kelland used an acoustic rangemeter, developed by John Partridge of Sonardyne, to produce a series of fixed datum points on the structure of the ship that were used as a basis for future surveying. The section drawings of the ship and the plans of the decks were then produced by manual trilateration and offset measurements. This was carried out mainly with thirty metre tapes (left) and one metre rules. Given that conditions on site were far from perfect, with poor visibility, strong currents, cold numb hands and plenty of structure and equipment to tangle tapes around, the results were very satisfactory.

 

Where possible, the deck planks and half beams were surveyed, and drawings prepared from these surveys, including details such as the fastenings. Parts of these surveys were never completed, as they had to be done before parts of the deck, particularly near the starboard side, had been excavated.

One part of the orlop deck had been dislodged during the past, and an in situ survey was not possible in the area affected.

The DSM system was developed by Nick Rule on the Mary Rose site. With this system an object is measured from four fixed points and the data is converted to x, y and z coordinates using custom-written software. The simplicity of the system allows divers who are inexperienced in survey techniques to produce useful data with a minimum amount of difficulty. It is particularly useful for measuring objects suspended in the silt that are not contiguous with the deck structures. The results can be shown on a conventional site plan with the depth in text, or can be modelled in 3D on a computer.

 

Both still and video photography (above) were used underwater, but there was one common problem, the Solent just isn't the Caribbean. Except on rare occasions, still photography of large areas of structure was rendered impossible by the limits of visibility.

 

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