A superb large scale chart of the Isle of Man with full topographical detail of the Isle of Man drawn from the Ordnance Survey. Large insets at the bottom detail Port St. Mary, Ramsey Bay and Castletown Bay, three further upper left feature Port Erin, Peel and Calf Sound. The chart also features the Decca system of navigation. An hyperbolic radio navigation system using fixed position radio beacons. Although invented in the USA it was developed by the British and deployed by the Royal Navy during the Second World War. It offered much better accuracy in coastal waters than previous systems. It was even used by aircraft in the post war era. It was eventually replaced by GPS in the 1990’s. Despite being a sea chart there is a wealth of topographical detail.