Page 122 - Manual for Activities directed at the Underwater Cultural Heritage

 Adriatic Sea played an important and irreplaceable role in establishing these trade routes.
effectively safeguarded, many good examples of maritime heritage will be lost forever. In stabilizing a site under water, the idea is to create an archive under water that is accessible and to make sure that the heritage is kept until this archive is opened. It is important to have an idea how long the protection has to be effective: for 5 years, 20 years or a hundred years. The protective measures have to be selected in a way that deterioration of the site can be reduced to a minimum and that it is still possible to access the site in the future for archaeological research. See Rule 24.
(d) Extraction. Objects should not be removed if there is no valid objective and not until secure arrangements have been made to conserve them properly out of the water. An underwater conservator needs to be on hand to ensure that adequate safeguards are in place when an extraction is carried out.
(e)Preventive conservation. As soon as an archaeological object is removed from the water, it begins to undergo physical and chemical processes that may result in major alteration and even destruction. It is thus essential for a conservation specialist to be on hand to see that the object is transported to the conservation laboratory under the best possible conditions. See Rule 24.
© Archivo del Centre d’Arqueologia Subaquàtica de Catalunya. Use of a laser beam to identify the sections of the ship Triunfante sunk in 1795 in Sant Père Pescador, Girona, Spain. Underwater archaeological explorations, which are being carried out both in shallow as well as in deep waters, need
an accurate positioning system for locating any artifact and to plot them on suitable scales. Several conventional methods and instruments are available for obtaining underwater positions in shallow water areas. But due to limitations under water like poor visibility conditions, etc. the diver archaeologists find difficulties in measuring angles and distances under water.
The laser track method that measures distance by timing the passage of a light pulse fired at
a target and its return can be applied effectively for shallow water archaeological surveys (max 15 m with a coverage of 5 km and a distance accuracy of 10 cm). 
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Objective, methodology and techniques