Major–General William Roy was the founder of the Ordnance Survey. He began his survey of England in 1783 while living at 10 Argyll Street in Soho.

EARLY MAP-MAKING

Roy, born in Lanarkshire, started working for the military survey of Scotland in 1747, by which time he was an accomplished surveyor and map-maker. Moving south in 1755, he joined the Army and carried out a reconnaissance survey of southern England. In 1765, after service in the Seven Years’ War, Roy was put in charge of military surveys in Britain.

THE ORDNANCE SURVEY

The Ordnance Survey can trace its beginnings back to 1783 when the President of the Royal Society, Sir Joseph Banks, commissioned Roy to take charge of an English survey. Its purpose was to determine the difference in longitude between Paris and London.

The starting point for this was a line, stretching for 5 miles (8km) eastwards from King’s Arbour on Hounslow Heath, and known as the ‘Hounslow Heath base’. By 1789 Roy had completed all the triangulation work between the base and the Kentish coast, making use of a theodolite specially crafted by the instrument maker Jesse Ramsden. Roy died at Argyll Street, having all but finished the last of three papers describing his surveying work for Philosophical Transactions.

The first public survey of Britain was set up by the Board of Ordnance in 1791, the year after Roy’s death. Using Roy’s fieldwork in southern England as its foundation, the Board produced its first map – of Kent – in 1801. The Ordnance Survey, as it is now known, continues to flourish to this day.