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Lanby buoy is a contraction of Large Automatic Navigation BuoY. Lanby buoys were first made in the USA by General Dynamics and adapted by Hawker Siddeley Dynamics for use in British waters in the early 1970s. The buoys were intended to replace lightships and were constructed as a circular hull with a central light to provide all-round visibility and a foghorn. They may also contain radio and radio beacons. The navigation buoy was to be monitored remotely from onshore and was designed to run for extended periods without repair. The running costs were estimated to be as little as 10% of those of a lightship.
However, experience showed that it was difficult to attain the required reliability in British waters due to the high acceleration forces experienced in rough seas with 14m waves and 7 knot currents. Alternative experiments were made with platforms such as the Royal Sovereign Lighthouse. The automatic technology was later used successfully in more conventional lightships.
A Lanby buoy replaced the Bar Lightship PLANET in the Mersey estuary in 1972 and remained in service for 21 years before being replaced itself.