Detailed British Admiralty chart of Sao Marco Bay, Brazil.

The chart marks soundings, hazards of the sea, and magnetic variation, lighthouses and beacons are highlighted in red and yellow, with principal ports and rivers marked. A course has been plotted in pencil.

Although the title states that the chart was based on French Government Surveys, these were most likely made by the French hydrographer Captain Ernest Mouchez (1821-1892). A large part of his surveying carrier was spent in China, Korea, and South America. In 1871, he was given the role of head of the Paris Observatory. The observatory had fallen into disrepair following the Franco-Prussian War, and Mouchez was partially successful in restoring its fortunes. Unfortunately, in 1887, he became heavily invested in a multi-national project to compile and index a photographic atlas of the heavens, the Carte du Ciel. The project consumed massive effort over several decades before it was rendered obsolete by modern astronomical methods.

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.