Detailed British Admiralty chart of southern Madagascar.

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

Britain at the beginning of the nineteenth century was beginning to look for an expansion of her trade along the east coast of Africa; in 1821 preparations were made at the Admiralty for an expedition to survey the African coast. The work was entrusted to Captain William Fitzwilliam Owen (1774-1857), and between 1822 and 1826, Owen surveyed much of the west, and east coasts of Africa, including Madagascar, the south coast of Arabia, and the River Gambia. Owen's work was not without incident, whilst in Muscat, he invited the Sultan on board the ships, but was therefore forced to temporarily tow away the huge number of pigs on board to avoid offending the Muslim Sultan; it is reported that the whole cove echoed with their squeals. These incidences aside, it was these surveys together with his work in the India Ocean (represented in the pilots here by: Nos. 598; 721; 594; and 595) that earnt him the respect of the Admiralty, who presented him with a silver punch-bowl in the form of a globe of the earth surmounted by Neptune and supported by figures representing the four continents.

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.