Admiralty chart

Admiralty charts are nautical charts issued by the United Kingdom Hydrographic Office (UKHO) and subject to Crown Copyright. Over 3,500 Standard Nautical Charts (SNCs) and 14,000 Electronic Navigational Charts (ENCs) are available with the Admiralty portfolio offering the widest official coverage of international shipping routes and ports, in varying detail. Admiralty charts have been produced by UKHO for over 200 years, with the primary aim of saving and protecting lives at sea. The core market for these charts includes over 40,000 defence and merchant ships globally. Today, their products are used by over 90% of ships trading internationally. The British admiralty charts are compiled, drawn and issued by the Hydrographic Office. This department of the Admiralty was established under Earl Spencer by an order in council in 1795, consisting of the Hydrographer, Alexander Dalrymple, one assistant and a draughtsman. The initial remit was to organise the charts and information in the office, and to make it available to His Majesty's ships. The Hydrographic Department began printing charts in 1800, with the acquisition of its first printing press. Initially charts were produced only for use by the Navy, but in 1821, Thomas Hurd, who had succeeded Dalrymple as Hydrographer in 1808, persuaded the Admiralty to allow sales to the public. The first catalogue of Admiralty charts was published in 1825, and listed 756 charts. Charts were printed from copper plates. Plates were engraved, in reverse, with a burin. The plate was inked, and the excess ink wiped from the flat surface before printing, so that ink remained only in the engraved lines (intaglio printing). The process allowed very fine detail to be printed, but was slow. When corrections or alterations were needed to a chart, the copper was hammered from behind, the raised section scraped and smoothed, and the new information engraved on the smoothed area. This allowed plates to continue in use for long periods, in some cases for over a hundred years.