Detailed British Admiralty chart of the Gulf of Thailand

The chart marks soundings, hazards of the sea, and magnetic variation, with principal ports and rivers marked.

The chart is principally based on the survey carried out by Mater John Richards, on board HMS Saracen in 1859. Saracen a brig sloop first launched in 1831, saw service as an anti slavery ship operating off the coast of west Africa between 1831 and 1839. In 1854, she was converted to a surveying vessel for use in southeast Asian waters.

The British Hydrographic Office was founded in 1795 by George III, who appointed Alexander Dalrymple as the first Hydrographer to the Admiralty. The first charts were produced in 1800. Unlike the U. S. Coast Survey the Hydrographic Office was given permission to sell charts to the public and they produced a great number of sea charts covering every corner of the globe. Most of the Admiralty charts produced by the Hydrographic Office delineated coastline as well as high and low water marks and record depth of water as established by soundings. In addition these charts included information on shoals, reefs, and other navigational hazards that plagued mariners across the world. Thanks to the innovations of Sir Francis Beaufort, who developed the Beaufort Scale of wind strength, the British Hydrographic Office became one of the leading producers of sea charts. In fact, such was their accuracy that the phrase 'Safe as an Admiralty Chart' was coined.