Real Experience of Locating Wrecks, by Pieter Bakker, Debbie Phillips and Sara Trillo Three NAS members were given the opportunity to witness what really happens when geophysicists go looking for shipwrecks. As locals to the Ramsgate area they are familiar with the vagaries of the weather which has been the cause of the hundreds of shipwrecks in the area. Early one morning in August three NAS members, Debbie, Pieter and Sara, met marine geophysicists Steph Arnott and Laura Andrews from Wessex Archaeology at Ramsgate Harbour to take part in their survey of the site of the sinking of the Royal Adelaide, a project commissioned by Historic England. The Royal Adelaide was a paddle-steamer owned by the City of Dublin Steam Packet Company, used as a ferry between London and Cork. It sank on 31st March 1850 off the Tongue Sands near Margate. The day before it had set sail from Plymouth carrying nearly 300 passengers. All those aboard were lost; many of them were Irish migrating to escape the famine. The Tongue Sands are only a few miles from Margate, tantalisingly close to the coast, but there was too much of a gale for the coastguards to be able to act upon the distress signals from the Royal Adelaide. We went out on Neptune, a twin-powered diesel engine catamaran, skippered by the very knowledgeable local skipper Dave Batchelor, and crew Brian Robinson. The day was calm - essential for the work to take place. The two previous days of poor weather had thwarted other attempts to visit the site. Neptune’s wheelhouse space was taken up with three carefully organised laptops for the survey, linking to a high precision GPS, a side-scan sonar, and a magnetometer. Steph and Laura worked non-stop during the twelve hours we were on Neptune. Marine Geophysicists Steph (left) and Laura (right) surrounded by technology on the search for wrecks They had to test that the equipment they were using to scan the seabed was working correctly before we started the survey. Both the magnetometer and side scan sonar, an Edgetech 4125, are referred to as tow-fish and were towed at the rear of the boat. After following the coast to Margate, then cutting across to Tongue Sands, we arrived at the presumed site of the Royal Adelaide wreck at 9.30 am. We used Neptune’s sonar to locate the wreck-site initially. Neptune has a single beam system telling the skipper the water depth below the keel. Once we were satisfied we had found the right site, the tow fish were deployed and towed at the rear of the boat at approximately 5 knots per hour, 5 metres above the seabed/wreck structure. Neptune towed the scanners over the wreck in parallel lines, ten lines east to west and two lines north to south. Images from the tow fish appeared on the lap tops as we watched with baited breath. The image below is from the side-scan sonar screen and show objects scattered over the seabed. Disturbance on the seabed detected by Neptune's sonar At the same time the magnetometer showed major disturbances of the earth's magnetic field This told us that these objects contained a lot of iron, and so were definitely made-made. As can be seen the scans that came up of the seabed were eerie: usually they looked like mosaics of burnt sienna brown colour, but when possible wreckage was located, darker marks and shapes appeared, and at one point there was a symmetrical repeated shape that obviously had a human/machine origin. Each sonar beam reaches about 40 m width. The distance between the lines was kept short to obtain ample overlap and ensure consistency of the information collected and to enhance the resolution of the images. In the post-processing of the information, the images will be stitched together. As the beam scans the seabed under 45 degrees angle the 'shadow' of each object changes on every pass, thus allowing for a three-dimensional impression as a final result. Scans were also undertaken of other sites of interest in the area - however no other structures were seen, so with the shifting nature of the sands it’s probable that these past sightings are now buried beneath sand. Steph and Laura were continuously recording all the information and once the scanning had finished they still had to gather up the tow fish and pack them up. We were full of admiration for how focussed and hard-working they were, especially as some of us took the opportunity to sit on deck and enjoy watching the changing sea colour and light formations, punctuated by views of the wind farm, coast, and a lone seal who followed the Neptune for a while. A massive thank you to Wessex Archaeology for allowing us to join them, and to Peta Knott and NAS for co-ordinating this trip for us; it was a fascinating insight into how much work goes into surveying possible wreck sites. Beautiful views like this reward those who work long hours at sea To discover what you could learn on our upcoming courses and events, click here. Have a story to tell? Find out about writing for us here.