Page 13: of Marine News Magazine (July 2011)

are usually about one to one and a half meters above the water in the fully laden condition. The transceivers are connected to a central processing unit by twin twisted pair cables. The CPU contains a dedicated processor that takes signals from the transceivers and the vessels GPS unit. It combines these with information about the vessels dimensions, and computes the positionof the water plane in real-time. This information is immediately available for processing and analysis. From this, the ADIS software calculates freeboard, draft, list, trim, tonnes to go and anyother parameter of interest to the mas- ter. The information is sent to a bridge display. The data can also be provided to a voyage data recorder. Unlike other models, ADIS sensors are mounted outside the hull above the waterline looking down.They are easily accessible for installation or maintenance andthere are no through-hull penetrations. Other benefits include improved fuel efficiency and handling. Vessels trimmed properly by the bow consume considerably less fuel. An incorrectly trimmed high-speed ferry may burn seven percent more fuel than the same vessel properly trimmed at the same speed. The ADIS can also prevent hog- ging and sagging that occurs in long,narrow ships, such as those on the Great Lakes. These types of vessels, if not carefully loaded in the correct sequence, can develop increased draft amidships (sagging) or increased draft at the bow and stern (hogging). In an extreme situation, the hull girder can fail. draft can also be optimized to allow for minimal clearance across the thresh- old of locks. Customers currently using ADIS include the U.S. Navy, for atti- tude control on floating missile launch platforms; British Columbia Ferries Corporation; Washington State Ferries; and the Alaska Marine Highway. www.weir-jones.com www.marinelink.com