SADI: indication of speed and deceleration to vessels in port approaches

In the early stages of a ship´s approach to port, adequate information on the vessel´s progress is available from shipborne equipment. In the berthing phase, speed and angle of approach is commonly available, for large ships, from shore-based instruments, sonar or radar. The author considers the problems facing large vessels in the intermediate phase, where the ship is decelerating, often in a limited width of fairway, and where violent changes in engine speed or rudder position can cause the vessel to sheer and run into the channel bank. He discusses the possibility of providing a shore-based visual signal that will enable the ship handler to regulate the vessel speed by comparison with some pre-planned deceleration profile. The design and operation of the speed and deceleration indicator (SADI) are presented