Page 107 - Manual for Activities directed at the Underwater Cultural Heritage

Like seismics, acoustic techniques, such as sides- can and multibeam sonar, are used for many purposes beyond heritage. Nevertheless, sidescans and multibeams are more regularly put to direct archaeological use. So are magnetometers and sub-bottom profilers. All such techniques acquire their data digitally and can be integrated with GPS position control so that the resulting images give amazing detail.
Sidescan sonar and GPS instruments come in different price ranges and are available for mounting on large and small research vessels or even rubber boats alike. In all instances, however, the equipment is only as good as its operator. In preliminary work, there is much to be said for combining di- fferent purposes in one survey, undertaken by technically competent operators in combination with ana-lysis by knowledgeable archaeologists. The de-veloper will want to know what kind of obstructions feature on the surface of the seabed and how they warrant the presence of archaeological sites. Side-scanning sonar can obviously be used for both, possibly followed by targeted survey to produce more detailed images by multibeam or video. Magnetometers show the presence of me- tal and can be deployed to locate metal in underwater
 © MMRG. A Knudsen 320 BP Echo-sounder in use over the port side of Zouhair 3, a small fishing boat, in the Oued Loukkos during the Morocco Maritime Survey investigation into the loca- tion of the ancient port of Lixus, Morocco.
A cockpit built of pvc pipes and plastic sheeting sheltered the elec- tronics used during the survey.
An example of a site potentially rich in underwater cultural heritage and concerned by intensive deve- lopment is the reclamation and offshore islands for housing along the coasts of Bahreïn, partly just offshore Qal’at al-Bahrain. The very extensive site was inscribed on the World Heritage list in 2005 as the Ancient Harbour and Capital of Dilmun. The offshore areas are outside the protection zone. Some have been surveyed and inventoried, but most have not, to the great concern of those presently integrating heritage values in planning.
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Preliminary work