There is no known portrait of William Roy and surprisingly little is known of his early life. We know he was born in Milton Head near Dalserf in South Lanarkshire in 1726. His father and grandfather were factors, supervising the property of the wealthy lairds of the Milton House Estate. He was a pupil in Carluke Parish and then at Lanark Grammar School. There is no record of university graduation from anywhere in Scotland. In 1746 however, he was co-opted by Lieutenant-Colonel David Watson to supervise the newly commissioned Military Survey of Scotland. His appointment to the Survey is an enigma. Roy was very young, we know nothing of his education, and Watson was an experienced senior army engineer who needed someone for a post which carried considerable technical and administrative responsibility. George Chalmers suggests that Roy may have studied surveying in the service of the Post Office. This is possible but unlikely. The Post Office Act of 1711 had prescribed regular road surveys but these were not extended to Scotland and there is no reference to his recruitment in early Post Office records. Arrowsmith suggests instead that he may have been a cadet at the Board of Ordnance in Edinburgh; cadets could be recruited as early as twelve years old. Colin MacLaurin, the eminent professor of mathematics at Edinburgh University was known to be interested in mapping and geodesic and to have been a regular visitor to the Board of Ordnance offices. EGR Taylor confirms this connection between Roy and MacLaurin and attributes Roy’s good grounding in mathematics and science to the influence of MacLaurin.
Roy was retained by Watson as an assistant quartermaster; this was a non-commissioned rank, at a time when even engineers were of warrant-officer grade. Despite this he assumed responsibility for the Military Survey for about eight years before being promoted to practitioner engineer. Shortly thereafter the Board changed its view and issued King’s commissions to engineers. Roy was appointed ensign to the 53rd Regiment of Foot . Fortunately the survey was almost completed . In 1756 the regiment was transferred to play its role in the Seven Years War. In 1759 Roy was promoted to captain, having been ‘noticed’ by the commander-in chief of the allied army at the Battle of Minden for his accurate and user-friendly geographical battle-plans. Thereafter his promotion was rapid. By 1765 he was quartermaster-general, surveyor-general of coasts and engineer-director of military surveys in Great Britain. He became full colonel in 1777 and major-general in 1781.
His career thereafter was largely based at the Quartermaster General’s Department at Horse Guards in London. In 1767 he presented a comprehensive proposal for a national survey of England- “ a good Military Plan or Map of the whole Country”, which he considered, “ best constructed during times of peace and tranquility.” The proposal incorporated methods, including “serieses of triangles” and also costings ( £20,000). Implementation was delayed because of expense and later, ironically, shelved because of the American War of Independence.
Roy was awarded the Copley Medal of the Royal Society in 1785 for his work determining the latitude and longitude of the French and English Royal Observatories. His most influential work was the topographical survey of Middlesex, Surrey, Kent and Sussex using his new Ramsden Theodolite, this leading to the principal of on-ground triangulation of Great Britain. Ramsden also designed for Roy a new, extremely accurate measuring chain - The Engineer’s Chain. Both men shared an interest in barometry. Roy experimented with Ramsden’s barometer on the summits of both Schiehallion in Scotland and Snowdon in Wales. He also had regular return visits to Scotland as an enthusiastic Roman historian. His various publications include his Military Antiquities of the Romans in Britain of which the drawings and maps remain an important resource.
William Roy died in London in 1790. He had long campaigned for a national mapping and survey service; the Ordnance Survey was established within a year of his death, and may be considered to be his legacy. His attention to accuracy, his careful method, his measured use of technology, science and mathematics prepared the way for modern geodesic survey practice. He is one of the fathers of modern surveying and cartography.