First obstacle avoidance sonar fitted to a tanker
Unlike conventional sonars that show the seabed directly beneath the keel, the See Echo looks ahead to provide an advance warning of any obstacles. It consists of two arrays that scan through a vertical arc of 20° and horizontally through a sector of 90°. They are linked to a dedicated high definition computer display on the ship’s bridge for ease of interpreting the sonar images. These are combined to create a three-dimensional representation of the sea ahead that can also be viewed with an electronic chart overlay. The system also provides a movable ‘camera’ viewpoint and is available with the option of target tracking. The display shows underwater objects, where they are in relation to the ship’s approach and their depth below the surface.
The See Echo system was developed by Marine Electronics in cooperation with the shipowner which had identified a need for a three-dimensional image of the sea up to 1km ahead of the vessel. The system is now undergoing a trials programme, following which, if successful, similar sonars will be installed onboard other ships in the company’s substantial fleet. Because the See Echo has been installed on a trial basis, the tanker operator has chosen to remain anonymous. However, a second system is now planned for installation on another ship in the fleet as soon as operating schedules permit.
Because the See Echo provides a three dimensional image, it has been found helpful for ships operating in sea ice. The display reveals the thickness of the ice sheet ahead and enables the ship’s master to decide whether it is possible to sail through it safely. This is expected to prove particularly important for cruise ships that are undertaking voyages into Polar waters. The sinking of the cruise ship Explorer in 2007 has confirmed the environmental and passenger safety risks that need to be guarded against.
The See Echo system was fitted inside the bulbous bow of the tanker during a dry-docking in Dubai. Installation required the design and construction of a sea chest inside the bow to accommodate the two sonar arrays. An acoustic window a little over 1m square was made from a kevlar and carbon fibre composite and fitted into the bow so that the transmissions from the sonar can leave and return to the ship unhindered. Despite presenting a flat surface at the ship’s bow, the size of the vessel is such that it has had no effect upon hydrodynamics or fuel consumption.
Installation of the See Echo on an operational tanker was prompted by the enormous costs that can be incurred by operators if a ship goes aground or is damaged in such a way as to cause pollution. Despite the comprehensive nature of modern hydrography, uncharted areas are known to persist.
The See Echo will also provide an alert for partially submerged objects such as cargo containers of which an estimated 10,000 are lost overboard every year. The sonar will register the presence of whales and other sea mammals that are in the path of the ship. The acoustic frequency of the transmissions from the sonar has been approved by NOAA in the USA as having little or no impact upon marine life.
