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Our history

Learn all about the history of our organisation, right from the time of the French Revolution through to the present day.

Since the 1700s Britain's landscape has changed beyond recognition; and we've changed too. Our video captures our story over the years, showing just how much we've evolved...


England was squeezed between rebellion in Scotland and war with France when King George II commissioned a military survey of the Scottish highlands in 1746. The job fell to William Roy, a far-sighted young engineer who understood the strategic importance of accurate maps, yet his vision of a national military survey wasn't implemented until after his death in 1790.

By then Europe was in turmoil, and there were real fears that the French Revolution might sweep across the English Channel. Realising the danger, the government ordered its defence ministry – the Board of Ordnance – to begin a survey of England's vulnerable southern coasts.

Military mapping

In June 1791, the Board purchased a huge new Ramsden theodolite, and surveyors began mapping southern Britain from a baseline that Roy himself had measured several years earlier.

The first one-inch map of Kent was published in 1801, and a similar map of Essex followed – just as Nelson's victory at Trafalgar made invasion less likely!

Within twenty years about a third of England and Wales had been mapped at the one-inch scale. If that seems slow in these days of aerial surveys and global positioning, spare a thought for Major Thomas Colby – later Ordnance Survey's longest serving Director General – who walked 586 miles in 22 days on a reconnaissance in 1819.

A taxing business

In 1824, Parliament ordered Colby and most of his staff to Ireland, to produce a detailed six inch to the mile valuation survey.

Colby designed specialist measuring equipment, established systematic collection of place names, and reorganised the map-making process to produce clear, accurate plans. But Colby the perfectionist also travelled with his men, helped to build camps, and arranged mountain-top feasts with huge plum puddings at the end of each surveying season.

Soon after the first Irish maps began to appear in the mid-1830s, the demands of the Tithe Commutation Act provoked calls for similar six-inch surveys in England and Wales. The government prevaricated but, by then, there was a new power in the land.

Driven by steam

This was the era of railway mania and if the one-inch map was unsuitable for calculating tithes, it was virtually useless for the new breed of railway engineers. To make matters worse, mapping of England and Scotland remained incomplete and, in 1840, the Treasury agreed that the remaining areas should be surveyed at the six-inch scale.

Now, surveyors needed greater access than ever before; and so, in 1841, the Ordnance Survey Act gave them a legal right to 'enter into and upon any land' for survey purposes.

London's burning!

A few months later Ordnance Survey's cramped Tower of London offices were at the centre of a national catastrophe when fire swept through the Grand Storehouse, threatening to engulf the Crown Jewels in the Martin Tower. Miraculously, the Jewels were saved, and most of Ordnance Survey's records and instruments were also carried to safety. But the blaze highlighted the Survey's desperate need for more office space, and prompted a move to Southampton.

The scene was now set for two decades of wrangling over scales. Throughout this period, Victorian reforming zeal was creating an acute need for accurate mapping. The issue was settled piecemeal until, by 1863, scales of six inches and twenty-five inches to the mile had been approved for mountain and moorland, and rural areas respectively. The one-inch map was retained, and detailed plans at as much as ten feet to the mile were introduced for built-up areas.

A new technology

By now, Major-General Sir Henry James – perhaps Ordnance Survey's most eccentric and egotistical Director General – was midway through his twenty-one year term. James quickly saw how maps could be cheaply and quickly enlarged or reduced using the new science of photography, and he designed an elaborate glass studio at Southampton for processing photographic plates.

James planted his name on everything he touched, and later claimed to have invented photozincography, a photographic method of producing printing plates. In fact, the process had been developed by two of his staff.

War and peace

Surveying during World War One

By 1895 the twenty-five inch survey was complete. The twentieth century brought cyclists and motorists swarming onto the roads, and the new Director General, Colonel Charles Close, prepared to exploit this expanding leisure market. But by now, the tide of history was sweeping Ordnance Survey back to its roots.

As Britain entered the First World War, surveyors, draughtsmen and printers from Ordnance Survey were posted overseas. Working in appalling conditions alongside the troops, surveyors plotted the lines of trenches and, for the first time, aerial photography was used to capture survey information.

Printing maps during World War One

After the war, Sir Charles, as he now was, returned to his marketing strategy and appointed a professional artist to produce eye-catching covers for the one-inch maps. Ellis Martin's classic designs boosted sales to record levels, but the war had taken its toll; behind their bright new covers, the maps were increasingly out of date.

A landmark review

In an uncanny echo of the mid-nineteenth century, a whole raft of new legislation brought demands for accurate, up-to-date mapping. Matters came to a head in 1935, and the Davidson Committee was established to review Ordnance Survey's future. That same year, a far-sighted new Director General, Major-General Malcolm MacLeod, launched the retriangulation of Great Britain.

Surveyors began an Olympian task, building the now familiar concrete triangulation pillars on remote hilltops throughout Britain. Deep foundations were dug by hand, and staff dragged heavy loads of materials over isolated terrain by lorry, packhorse and sheer brute force.

The Davidson Committee's final report set Ordnance Survey on course for the 21st century. The National Grid reference system was introduced, using the metre as its measurement. An experimental new 1:25,000 scale map was launched, leaving only the one-inch unscathed. It was almost forty years before this popular map was superseded by the 1:50,000 scale series, first proposed by William Roy more than two centuries earlier.

Bombed out!

In 1939, war intervened once again. The Royal Artillery was now responsible for its own field surveys, but over a third of Ordnance Survey's civilian staff were called up, and its printing presses were kept busy with war production.

It wasn't a soft option. Enemy bombing devastated Southampton in November 1940 and destroyed most of Ordnance Survey's city centre offices. Staff were dispersed to other buildings, and to temporary accommodation at Chessington.

Ordnance Survey and military units – British, Canadian and American – were directed to produce new maps of Europe, as well as revise old ones.

In the event of a major war, it was always assumed that Ordnance Survey would limit its civilian activities and concentrate on military work. The military appetite remained insatiable - the Normandy landings alone devoured 120 million maps!

Coming home

After the war, Ordnance Survey returned to Davidson's agenda; the retriangulation was completed, and metric maps began to appear along National Grid sheet lines. Aerial survey helped speed up the new continuous revision strategy, and up-to-date drawing and printing techniques were introduced.

But the organisation was still fragmented, scattered across southern England in a battered collection of worn-out buildings. All that changed in 1969, when Ordnance Survey moved to a purpose-built head office on the outskirts of Southampton, on Romsey Road. Four years later, the first computerised large-scale maps appeared; the digital age had begun.


Technology advances brought about by the advent of the computer were not the only changes in this period as changes in status gradually saw the organisation become progressively market led. In 1974 the position of Ordnance Survey Director General became a civilian post, and in 1983 it became a wholly civilian organisation, with a further change in status in 1999 when the agency became a government trading fund.

Ordnance Survey digitised the last of some 230,000 maps in 1995, making Britain the first country in the world to complete a programme of large-scale electronic mapping. Computers have transformed the map-making process, and electronic data is now routinely available to customers within 24 hours of being surveyed.

In 2001, the agency launched yet another innovation. A multi-million pound project established a seamless information base which underpins a new generation of detailed data called OS MasterMap. This intelligent geospatial database makes it even easier for other people's information to be integrated in to it, held as separate layers, or linked to Ordnance Survey mapping. Data from OS MasterMap® offers definitive, consistent and maintained referencing to more than 440 million man-made and natural landscape features in Britain. In addition to topographic mapping, other layers of information have been added progressively to OS MasterMap®, such as aerial photographic images which precisely match the mapping; data providing the addresses of all properties; and integrated transport information.

Today – and the future

Our present head office is just off the M271, following another move in 2010.

At OS we’ve changed from a centuries-old venerable mapping company into a big data powerhouse. Our location data – or geographic information (GI) – has weaved itself into the very fabric of everyday life, right across Great Britain. While the public still knows us for our comprehensive range of printed leisure maps, the digital side of the business accounts for more than 80% of turnover.

The public and private sectors benefit from accurate information about ‘location’ and a world-leading reliable geographic framework helps deliver effective and efficient services.

The majority of information collected in Britain has some geographic feature – from the location of people, buildings and postcodes to administrative boundaries and flood risk areas. The potential to help make businesses more profitable and efficient through linking and analysing different sets of information is enormous.

Major investments have been made to help us collect and maintain richer data. This is achieved today through field surveyors, global navigation satellite systems, remote sensing and a range of advanced geographical information systems (GIS) tools and software.

All 243,241 square kilometres of Great Britain are surveyed and up to 10,000 changes are put into the database daily.

The company vision is that we at OS, and our partners, reveal our ever-changing landscape in extraordinary detail, giving the most comprehensive view of Britain.

With effect from 1 April 2015 we have operated as a Government owned limited company, the entire issued share capital of which is held by the Secretary of State for Business, Innovation and Skills (BIS).

See also

Marking the centenary of WW1 with BBC’s Countryfile

In Countryfile's World War One special, we explored what life would have been like for surveyors on the western front.

Normally published near the beginning of July, our Annual Report and Accounts documents our major business events and finances for the year to 31 March.

View a timeline of events in Ordnance Survey's 220-year history.

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