Optimal sidescan sonar and subbottom profiler surveying of ancient wrecks: The ‘Fiskardo’ wreck, Kefallinia Island, Ionian Sea

Abstract Marine geophysical data collected during an underwater natural and cultural heritage assessment survey along the coastal zone of Kefallinia Island in the Ionian Sea, Greece, showed among other seafloor features, the presence of a Roman shipwreck and its amphorae cargo on the seafloor. The study and analysis of the collected data demonstrated that: (i) sidescan sonar and chirp sub-bottom profiling systems, can successfully detect ancient shipwrecks and their amphorae cargo on the seafloor, (ii) the use of objective computer vision techniques in processing sidescan sonar seafloor images, is a valuable tool for the separation of potential ancient shipwreck targets from other seafloor features with similar acoustic signatures. Furthermore, a guideline for the data acquisition parameters that should be used to obtain optimal seafloor sonar images to maximize the separation of potential shipwreck targets from other seafloor features, is provided. The underwater sonar remote sensing techniques may also provide adequate indication regarding the amphorae hull stowage and its vulnerability to human activity in the area. The shipwreck is dated between 1st century BC and 1st century AD and is one of the largest found so far in the Mediterranean Sea, for that period. It is estimated that it was carrying about 6,000 amphorae. The amphorae cargo, visible on the seafloor, is in very good state of preservation and the shipwreck has the potential to yield a wealth of information about the shipping routes, trading, amphorae hull stowage and ship construction during the relevant period and is therefore considered to be of significant archaeological importance.