This August a Gavia Autonomous Underwater Vehicle (AUV) was deployed by the Icelandic Coast Guard (ICG) to positively identify a contact observed during previous operations in autumn 2009. Routine bathymetric surveys then found a ship-like shape in an area where in November 1944 two ships, the British oiler SS Shirvan and the Icelandic steamship Godafoss were sunk by a German submarine U-300. The new shape seen was roughly the same length as the SS Shirvan.
During the August 2010 mission conducted by the Icelandic Coast Guard with the cooperation of the University of Iceland, a Gavia vehicle investigated the target using a range of acoustic sensors including a high-frequency side scan and a swath bathymetry system. Once in the vicinity of the target, the Gavia vehicle was deployed from one of ICG cutter Tyr's small boats and quickly revealed that the potential target was indeed a ship rather than a geographic feature after an initial side-scan survey ran at greater than normal altitudes designed to chart hazards such as any fishing nets and masts.
Further dives by the Gavia vehicle on the same day gathered considerable data from both the 600kHz and the higher frequency 1200kHz Side Scan. A 500kHz Gavia mounted GeoSwath system from GeoAcoustics, provided detailed bathymetry of the wreck and surrounding area.
The Shirvan was hit by two torpedoes and burned for 24 hours before sinking which resulted in considerable damage to the wreck. It was found to be broken into three sections, with signs of considerable deterioration of the hull, allowing some interior structures to be seen. Despite the damage, the detailed high-frequency sonar imagery meant it was possible to identify the wreck based on several identifiable features, particularly in the better-preserved aft most section.
According to shipping manifests, the Shirvan was carrying a full load of oil or gasoline when she sank, and thus it was feared that if the 6,000 ton vessel was intact, there could potentially be a significant environmental issue associated with the leaking fuel. Utilising the data from the Gavia AUV the Icelandic Coast Guard was able to determine that due to the condition of the wreck it is highly unlikely any significant quantities of gasoline remain onboard.
According to Captain Halldór Nellet, Chief of Operations of the Icelandic Coast Guard, the Gavia AUV proved to be an invaluable asset during this operation to identify the contact that was earlier discovered. Within 20 minutes of the initial dive ascertained was that this contact was a ship, and data gathered from subsequent dives helped us to positively identify it as the SS Shirvan and to alleviate concerns about the potential ramifications of a wreck with a full load of oil so close to the coast.
The finding of the Shirvan is historically significant, as the exact location where the Shirvan went down has until known been unknown and the Icelandic Goðafoss was lost in the same attack after she defied orders and stopped to rescue the British sailors on the Shirvan. This action resulted in a significant loss of life amongst both the crew of Godafoss and the rescued crewmen from the Shirvan, to date, despite numerous attempts, the wreck of the Godafoss remains undiscovered. However, locating the wreck of the Godafoss may not be imminent as the stricken Shirvan drifted for roughly 24 hours after the attacks on the two vessels.
Demo of RIEGL Airborne Bathy Scanner in Camcopter UAV
It's not an AUV but a UAV. So an unmanned vehicle, but in the air instead of underwater. This movie shows a demonstration of the bathymetric laser scanning capabilities of the RIEGL VQ-820-GU hydrographic airborne sensor in reality. For more information on the technical side, please see the news release on Hydro International.