Ordnance Survey

Ordnance Survey (OS) is the national mapping agency for Great Britain.

The first national mapping agency was the Ordnance Survey in the United Kingdom; its roots go back to 1747, when the compilation of a map of the Scottish Highlands was proposed.

Among Watson's assistants were William Roy, Paul Sandby and John Manson.

It was Roy's advocacy and leadership that led to the creation of the Ordnance Survey in 1791, the year after his death.

The agency's name indicates its original military purpose (see ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of 1745.

In 1784, a team from General William Roy's Ordnance Survey of Great Britain began the Principal Triangulation of Britain.

It was hard work: Major Thomas Colby, the longest-serving Director General of Ordnance Survey, walked 586 mi in 22 days on a reconnaissance in 1819.

Thomas Frederick Colby FRS FRSE FGS FRGS (1 September 1784 – 9 October 1852), was a British major-general and director of the Ordnance Survey (OS).

In the next 20 years about a third of England and Wales was mapped at the same scale (see Principal Triangulation of Great Britain) under the direction of William Mudge, as other military matters took precedence.

William Mudge (1762–1820) was an English artillery officer and surveyor, born in Plymouth, an important figure in the work of the Ordnance Survey.

After a fire in the Tower of London, the headquarters of the survey was moved to Southampton, and Yolland was put in charge, but Hall sent him off to Ireland so that when Hall left in 1854 Yolland was again passed over in favour of Major Henry James.

The former offices of Ordnance Survey are situated in London Road, Southampton, close to the junction with The Avenue, and are now part of the city's court complex and are occupied by Government agencies.

Roy later had an illustrious career in the Royal Engineers (RE), rising to the rank of General, and he was largely responsible for the British share of the work in determining the relative positions of the French and British royal observatories.

Although mapping by what became the Ordnance Survey was born out of military necessity it was soon realised that accurate maps could be also used for civil purposes.

In 1801 the first one-inch-to-the-mile (1:63,360 scale) map was published, detailing the county of Kent, with Essex following shortly afterwards.

As an indication of the area's military importance, the first Ordnance Survey map ever drawn was a one-inch map of Kent, published in 1801.

Following a fire at its headquarters at the Tower of London in 1841 the Ordnance Survey relocated to a site in Southampton and was in disarray for several years, with arguments about which scales to use.

Significant employers in the city include Southampton City Council, the University of Southampton, Solent University, Southampton Airport, Ordnance Survey, BBC South, the NHS, Associated British Ports (ABP) and Carnival UK.

Similarly, the spelling of Scafell and Scafell Pike copied an error on an earlier map, and was retained as this was the name of a corner of one of the Principal Triangles, despite "Scawfell" being the almost universal form at the time.

Below Rough Crag and Pen is a further tier, named Dow Crag and Central Pillar on Ordnance Survey maps, although known as Esk Buttress among climbers.

From the 1840s, the Ordnance Survey concentrated on the Great Britain "County Series", modelled on the earlier Ireland survey.

The Ordnance Survey Great Britain County Series maps were produced from the 1840s to the 1890s by the Ordnance Survey, with revisions published until the 1940s.

The primary triangulation of the United Kingdom of Roy, Mudge and Yolland was completed by 1841, but was greatly improved by Alexander Ross Clarke who completed a new survey based on Airy's spheroid in 1858, completing the Principal Triangulation.

He was an officer of the Royal Engineers employed on the Ordnance Survey.

When Colby retired he recommended William Yolland as his successor, but he was considered too young and the less experienced Lewis Alexander Hall was appointed.

After service in Britain, Ireland and Canada he was posted to the Ordnance Survey in 1838.

In 1920 O. G. S. Crawford was appointed Archaeology Officer and played a prominent role in developing the use of aerial photography to deepen understanding of archaeology.

For most of his career the archaeological officer of the Ordnance Survey (OS), he wrote a range of books on archaeological subjects and was a keen proponent of aerial archaeology.

After the war, Colonel Charles Close, then Director General, developed a strategy using covers designed by Ellis Martin to increase sales in the leisure market.

For most of his working life he was employed by Britain's map making organisation the Ordnance Survey, for which he performed painting, drawing and calligraphy for their map and book covers, and for their advertisements.

Roy's birthplace near Carluke in South Lanarkshire is today marked by a memorial in the form of a large OS trig point.

After the war, Colonel Charles Close, then Director General, developed a strategy using covers designed by Ellis Martin to increase sales in the leisure market.

He was Director General of the Ordnance Survey from 1911 to 1922.

After a fire in the Tower of London, the headquarters of the survey was moved to Southampton, and Yolland was put in charge, but Hall sent him off to Ireland so that when Hall left in 1854 Yolland was again passed over in favour of Major Henry James.

Major-General Sir Henry James FRS MRIA (1803–1877) was a Royal Engineers officer who served as the director-general of the Ordnance Survey, the British Government mapping agency, from 1854 to 1875.

After the Ordnance Survey published its first large-scale maps of Ireland in the mid-1830s, the Tithe Commutation Act 1836 led to calls for a similar six-inch to the mile survey in England and Wales.

It and the Ordnance Survey of Northern Ireland (OSNI) are the ultimate successors to the Irish operations of the British Ordnance Survey.

The British Geological Survey was founded in 1835 as the Ordnance Geological Survey under Henry De la Beche, and remained a branch of the Ordnance Survey until 1965.

It remained a branch of the Ordnance Survey for many years.

The new Director General, Major-General Malcolm MacLeod, started the retriangulation of Great Britain, an immense task involving the erection of concrete triangulation pillars ("trig points") on prominent hilltops as infallible positions for theodolites.

Major-General Malcolm Neynoe MacLeod (23 May 1882–1 August 1969) was Director General of the Ordnance Survey from 1935 to 1943.

The primary triangulation of the United Kingdom of Roy, Mudge and Yolland was completed by 1841, but was greatly improved by Alexander Ross Clarke who completed a new survey based on Airy's spheroid in 1858, completing the Principal Triangulation.

Although his measurements were superseded by more accurate radius figures (such as those used for GRS 80 and WGS84) his Airy geoid (strictly a reference ellipsoid, OSGB36) is still used by Great Britain's Ordnance Survey for mapping of England, Scotland and Wales because it better fits the local sea level (about 80 cm below world average).

By 1791 the Board received the newer Ramsden theodolite (an improved successor to the one that Roy had used in 1784), and work began on mapping southern Great Britain using a five-mile baseline on Hounslow Heath that Roy himself had previously measured; it crosses the present Heathrow Airport.

On completion of the Survey the theodolite was stored in the headquarters of the Ordnance Survey at Southampton where it was destroyed in the bombing raids of 1941.

By 1791 the Board received the newer Ramsden theodolite (an improved successor to the one that Roy had used in 1784), and work began on mapping southern Great Britain using a five-mile baseline on Hounslow Heath that Roy himself had previously measured; it crosses the present Heathrow Airport.

The eventual mapping of the whole of the United Kingdom by the Ordnance Survey began with the measuring of an accurate base-line on Hounslow Heath, chosen for its flatness and its relative proximity to the Royal Greenwich Observatory.

The British Geological Survey was founded in 1835 as the Ordnance Geological Survey under Henry De la Beche, and remained a branch of the Ordnance Survey until 1965.

The government then appointed De la Beche to work with the Ordnance Survey.