An extremely detailed chart of the best routes from Calcutta down the coast of the Malay Peninsula, through the Malacca Strait to the "Sincapour" Strait and beyond. The map extends are far northeast as Hainan, and includes western Borneo and Java. Horsburgh was very familiar with the waters shown in the chart, having spent more than twenty years sailing them.
James Horsburgh's (1762-1836) first voyages were from Newcastle and the Firth of Forth to Hamburg, Middelburg, and Ostend. After a relatively tame beginning, his life at sea became seriously adventurous when he was captured off Walcheren by a French privateer in May of 1780, and imprisoned for a short time in Dunkirk. Shortly afterwards, he sailed to the West Indies with the crew of an Austrian vessel. Back in London in 1782, he narrowly avoided being press-ganged by pretending to be Danish. In 1783, he was booked passage to India, but was nearly swept out to sea, when he decided to swim to back to shore as the ship was leaving the Hooghly River.
From then, until his retirement in 1805, Horsburgh sailed with various crews plying a trade between India and China. During this time, he was briefly shipwrecked on the island of Diego Garcia, and was given command of the Anna, in April 1798, in which he made several voyages to Canton, gaining valuable firsthand experience of the treacherous shoals, winds, and currents in the China Sea.
His mentor, collaborator, and friend, Alexander Dalrymple, had been hydrographer to the Admiralty and the East India Company. After his sudden death in 1810, Horsburgh offered to replace him in his role with the East India Company. As hydrographer Horsburgh was "primarily responsible for supervising the engraving of charts sent back to London by marine surveyors in India and ordered by the company to be published, and for examining the deposited journals of returning ships for observations which would refine the oceanic navigation charts currently in use, besides other duties of provision of information laid on him by the court. He continued privately to revise and republish his sailing directions, subsequently known as the 'East India Directory'... With the demise of the East India Company and of the Indian navy in 1858 and 1863, many of the charts Horsburgh had published were taken over by the hydrographic office and issued as admiralty charts" (Andrew S. Cook for ODNB).