Easytrak Contributes to Laying Operation

The Easytrak Portable USBL system has, since its launch in 2004, continued to evolve, operating in many applications, and remaining true to its origins. Oceanteam 2000 Ltd (ot2k) selected the Easytrak for its set-up time and portability for use as part of its mattress laying operations in The North Sea. Mattresses are heavy concrete structures used to shield cables on the seabed. The contract was to protect the cables which run from two offshore wind farms at Scroby Sands and Noordsee Wind in very shallow water, between 15 and 25 metres in depth. Prior to starting the mattress laying at Scroby Sands, the Easytrak system was used with a tracked ROV to determine cable locations. The mattresses were deployed from a vessel on four point mooring, using a lifting frame with a transponder at each end and sub-surface gyro to monitor heading. A scanning sonar mounted on a seabed frame was used to check mattress positions relative to each other. When married to high precision GPS (either RTK or HP DGPS) and motion sensors, absolute accuracies in the order of 2 - 2.5m, and relative accuracies of better than 1m in 25m of water were achieved.