Geophysical Techniques For Maritime Archaeological Surveys

Over the last ten years, the high-resolution marine geophysical survey field has witnessed<br>significant advances in survey investigation equipment. New equipment is based on acoustic,<br>optical, electrical, and magnetic sensors. This paper will focus on the use of quantitative acoustic<br>methods for the high-resolution mapping of the seafloor for archaeological heritage management. In<br>particular multibeam sonar and acoustic ground discrimination sonar (agds) were tested at two<br>historic wreck sites on the UK shelf, namely the Stirling Castle, Goodwin Sands, England and the<br>SMS Cöln, Scapa Flow, Scotland. At both sites, acoustic reflection amplitude values were mapped<br>using the single beam sonar over each wreck site and in the immediate wreck vicinity. The<br>amplitude values were analysed with respect to the 3D topography of the site obtained mapped from<br>very high resolution bathymetric surveying using the multibeam sonar. Subsequent ground truth<br>inspection based on the maps produced from the agds and multibeam sonar was carried out using<br>both diver and ROV observations. Correlations obtained between the remote geophysical surveying<br>and the ground truth observations provided new insight into the current state of the wrecks and the<br>wreck site stability. With increasing pressure on the near shore zone from leisure activities, the<br>extraction industry and environmental changes, there is a great need for rapid mapping and<br>evaluation techniques. Thus the information provided by remote geophysics can be of great benefit<br>not only for mapping what is in these zones today but also for future long-term management of the<br>archaeological heritage.