Ordnance Survey
The Ordnance Survey is the national mapping agency for Great Britain. The agency's name indicates its original military purpose, which was to map Scotland in the wake of the Jacobite rising of 1745. This work was also driven by a more general and nationwide need in light of the potential threat of invasion during the Napoleonic Wars. Since 1 April 2015, the Ordnance Survey has operated as Ordnance Survey Ltd, a government-owned company, 100% in public ownership. The Ordnance Survey Board remains accountable to the Secretary of State for Science, Innovation and Technology. It was also a member of the Public Data Group.
Paper maps represent only 5% of the company's annual revenue. It produces digital map data, online route planning and sharing services and mobile apps, plus many other location-based products for business, government and consumers. Ordnance Survey mapping is usually classified as either "large-scale" or "small-scale". The Survey's large-scale mapping comprises 1:2,500 maps for urban areas and 1:10,000 more generally. These large scale maps are typically used in professional land-use contexts and were available as sheets until the 1980s, when they were digitised. Small-scale mapping for leisure use includes the 1:25,000 "Explorer" series, the 1:50,000 "Landranger" series and the 1:250,000 road maps. These are still available in traditional sheet form.
Ordnance Survey maps remain in copyright for 50 years after their publication. Some of the copyright libraries hold complete or near-complete collections of pre-digital OS mapping.
History
Origins
The origins of the Ordnance Survey lie in the aftermath of the Jacobite rising of 1745. Prince William, Duke of Cumberland realised that the British Army did not have a good map of the Scottish Highlands to locate Jacobite dissenters such as Simon Fraser, 11th Lord Lovat so that they could be put on trial. In 1747, Lieutenant-Colonel David Watson proposed the compilation of a map of the Highlands to help in pacifying the region. In response, King George II charged Watson with making a military survey of the Highlands under the command of the Duke of Cumberland. Among Watson's assistants were William Roy, Paul Sandby and John Manson. The survey was produced at a scale of 1 inch to 1,000 yards and included "the Duke of Cumberland's Map", now held in the British Library.Roy later had an illustrious career in the Royal Engineers, 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. This work was the starting point of the Principal Triangulation of Great Britain, and led to the creation of the Ordnance Survey itself. Roy's technical skills and leadership set the high standard for which the Ordnance Survey became known. Work was begun in earnest in 1790 under Roy's supervision, when the Board of Ordnance began a national military survey starting with the south coast of England. Roy's birthplace near Carluke in South Lanarkshire is today marked by a memorial in the form of a large OS trig point.
By 1791, the Board received the newer Ramsden theodolite, and work began on mapping southern Great Britain using a baseline on Hounslow Heath that Roy himself had previously measured; it crosses the present Heathrow Airport. In 1991, Royal Mail marked the bicentenary by issuing a set of postage stamps featuring maps of the Kentish village of Hamstreet.
In 1801, the first one-inch-to-the-mile map was published, detailing the county of Kent, with Essex following shortly afterwards. The Kent map was published privately and stopped at the county border, while the Essex maps were published by the Ordnance Survey and ignored the county border, setting the trend for future Ordnance Survey maps.
During the next 20 years, about a third of England and Wales was mapped at the same scale under the direction of William Mudge, as other military matters took precedence. It took until 1823 to re-establish the relationship with the French survey made by Roy in 1787. By 1810, one-inch-to-the-mile maps of most of the south of England were completed, but they were withdrawn from sale between 1811 and 1816 because of security fears. By 1840, the one-inch survey had covered all of Wales and all but the six northernmost counties of England.
Surveying was hard work. For instance, Major Thomas Colby, the longest-serving Director General of the Ordnance Survey, walked in 22 days on a reconnaissance in 1819. In 1824, Colby and most of his staff moved to Ireland to work on a six-inches-to-the-mile valuation survey. The survey of Ireland, county by county, was completed in 1846. The suspicions and tensions it caused in rural Ireland are the subject of Brian Friel's play Translations, written in 1980.
Colby was not only involved in the design of specialist measuring equipment. He also established a systematic collection of place names, and reorganised the map-making process to produce clear, accurate plans. Place names were recorded in "Name Books", a system first used in Ireland. The instructions for their use were:
Whilst these procedures generally produced excellent results, mistakes were made: for instance, the Pilgrims' Way in the North Downs labelled the wrong route, but the name stuck. 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. Colby believed in leading from the front, travelling with his men, helping to build camps and, as each survey session drew to a close, arranging mountain-top parties with enormous plum puddings.
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. At the same time, the uneven quality of the English and Scottish maps was being improved by engravers under Benjamin Baker. By the time Colby retired in 1846, the production of six-inch maps of Ireland was complete. This had led to a demand for similar treatment in England, and work was proceeding on extending the six-inch map to northern England, but only a three-inch scale for most of Scotland.
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 a fire in the Tower of London, the headquarters of the survey was moved to Southampton taking over buildings previously occupied by a military orphanage in 1841, 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. Hall was enthusiastic about extending the survey of the north of England to a scale of 1:2,500. In 1855, the Board of Ordnance was abolished and the Ordnance Survey was placed under the War Office together with the Topographical Survey and the Depot of Military Knowledge. Eventually in 1870 it was transferred to the Office of Works.
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. The following year, he completed an initial levelling of the country.
Great Britain "County Series"
After the Ordnance Survey published its first large-scale maps of Ireland in the mid-1830s, the Tithe Act 1836 led to calls for a similar six-inch to the mile survey in England and Wales. Official procrastination followed, but the development of the railways added to pressure that resulted in the . This granted a right to enter property for the purpose of the survey. 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. Major-General Sir Henry James was by then Director General, and he saw how photography could be used to make maps of various scales cheaply and easily. He developed and exploited photozincography, not only to reduce the costs of map production but also to publish facsimiles of nationally important manuscripts. Between 1861 and 1864, a facsimile of the Domesday Book was issued, county by county; and a facsimile of the Gough Map was issued in 1870.From the 1840s, the Ordnance Survey concentrated on the Great Britain "County Series", modelled on the earlier Ireland survey. A start was made on mapping the whole country, county by county, at six inches to the mile. In 1854, "twenty-five inch" maps were introduced with a scale of 1:2500 and the six inch maps were then based on these twenty-five inch maps. The first edition of the two scales was completed by the 1890s, with a second edition completed in the 1890s and 1900s. From 1907 till the early 1940s, a third edition was begun but never completed: only areas with significant changes on the ground were revised, many two or three times. Meanwhile, publication of the one-inch to the mile series for Great Britain was completed in 1891.
From the late 19th century to the early 1940s, the OS produced many "restricted" versions of the County Series maps and other War Department sheets for War Office purposes, in a variety of large scales that included details of military significance such as dockyards, naval installations, fortifications and military camps. Apart from a brief period during the disarmament talks of the 1930s, these areas were left blank or incomplete on standard maps. The War Department 1:2500s, unlike the standard issue, were contoured. The de-classified sheets have now been deposited in some of the Copyright Libraries, helping to complete the map-picture of pre-Second World War Britain.