Ordnance Survey facts for kids
| Welsh: Arolwg Ordnans | |
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| Agency overview | |
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| Formed | 1791 |
| Jurisdiction | Great Britain |
| Headquarters | Southampton, England, UK 50°56′16″N 1°28′17″W / 50.9378°N 1.4713°W |
| Employees | 1,244 |
| Minister responsible |
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| Agency executive |
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| Parent agency | Department for Science, Innovation and Technology |
| Website | |
The Ordnance Survey (OS) is the official map-making group for Great Britain. Its name comes from its first job, which was military. "Ordnance" means military supplies, like artillery. The agency started by mapping Scotland after a rebellion in 1745. There was also a need for maps across the country. This was due to the threat of invasion during the Napoleonic Wars.
Since 2015, Ordnance Survey has been a company owned by the government. It is 100% publicly owned. The Ordnance Survey Board reports to the Secretary of State for Science, Innovation and Technology.
Today, paper maps make up only a small part of the company's income. Most of its work involves digital map data. This includes online route planning and mobile apps. They also create many other location-based products. These are used by businesses, the government, and everyday people. Ordnance Survey maps are either "large-scale" or "small-scale." Large-scale maps are very detailed. They are used for things like planning land use. Small-scale maps are for fun activities like hiking.
Ordnance Survey maps are protected by copyright for 50 years. This means they cannot be copied freely until then. Some special libraries keep full collections of old OS maps.
Contents
History of Ordnance Survey Maps
How Mapping Began
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This is a detailed part of a 1901 map. It shows St. George's Town in Bermuda. The map was made from surveys done between 1897 and 1899.
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The Ordnance Survey started after a rebellion in Scotland in 1745. Prince William, Duke of Cumberland, realized the army needed better maps. They needed to find rebels in the Scottish Highlands. In 1747, Lieutenant-Colonel David Watson suggested making a map of the Highlands. This would help control the clans.
King George II asked Watson to create a military survey. William Roy was one of Watson's helpers. This survey led to "the Duke of Cumberland's Map." It is now kept in the British Library.
Roy later became a General in the Royal Engineers. He was very important in mapping the distance between French and British observatories. This work started the main survey of Great Britain. It also led to the creation of the Ordnance Survey itself. Roy's skills helped set the high standards for the OS.
Work began in 1790 under Roy. The Board of Ordnance started a national military survey. It began on the south coast of England. In 1791, they got a new, improved measuring tool called a theodolite. Mapping southern Great Britain began using a 5-mile baseline. This line crossed what is now Heathrow Airport.
In 1801, the first one-inch-to-the-mile map was published. It showed the county of Kent. Soon after, Essex was mapped. The Kent map was private and stopped at the county line. But the Essex maps were from Ordnance Survey. They crossed county lines, setting a new standard.
Over the next 20 years, about a third of England and Wales was mapped. This was at the same scale. Other military needs took priority. By 1810, most of southern England was mapped. But these maps were taken off sale for a few years due to security fears. By 1840, almost all of England and Wales was covered.
Surveying was very difficult work. For example, Major Thomas Frederick Colby was a long-serving Director General. In 1819, he walked 586 miles in 22 days just to explore. In 1824, Colby and his team moved to Ireland. They worked on a detailed survey there. This survey of Ireland was finished in 1846.
Colby also created a system for collecting place names. He made sure names were spelled correctly. This system was first used in Ireland. Surveyors had to check different sources for names. They wrote down how names were commonly spelled. They also noted other spellings and where they found them.
Sometimes, mistakes were made. For example, the Pilgrims' Way was labeled on the wrong path. But the name stuck. Also, the spelling of Scafell and Scafell Pike copied an old error. Even though "Scawfell" was common, the error was kept. Colby was a strong leader. He traveled with his men and even helped build camps.
In 1835, the British Geological Survey was formed. It was part of the Ordnance Survey until 1965. In 1841, the Ordnance Survey moved its main office to Southampton. This happened after a fire at the Tower of London. By the time Colby retired in 1846, the six-inch maps of Ireland were done.
Mapping Great Britain by County
After mapping Ireland, people wanted similar detailed maps for England and Wales. The Ordnance Survey Act 1841 allowed surveyors to enter private land. This helped with the survey. After the fire in London, the OS moved to Southampton. There were debates about which map scales to use.
Major-General Sir Henry James became Director General. He found a way to use photography to make maps cheaply. This method was called photozincography. It helped reduce costs. It also allowed them to print copies of important old documents. For example, they printed a copy of the Domesday Book.
From the 1840s, the Ordnance Survey focused on the "County Series" for Great Britain. This was like the earlier Ireland survey. They started mapping the whole country, county by county. The scale was six inches to the mile (1:10,560). In 1854, even more detailed "twenty-five inch" maps were introduced. These were at a scale of 1:2500. The six-inch maps were then based on these.
The first versions of these maps were finished by the 1890s. A second version was completed around 1900. A third version started in 1907 but was never fully finished. Only areas with big changes were updated. The one-inch to the mile series for Great Britain was finished in 1891.
From the late 1800s to the early 1940s, OS made "restricted" maps. These were for the military. They showed details like dockyards and military camps. These areas were left blank on regular maps. Now, these de-classified maps are available in some libraries. They help complete the map picture of Britain before World War II.
Mapping Cities and Towns
In 1824, OS started a 6-inch survey of Ireland for taxes. But this wasn't detailed enough for cities. So, they used a five-foot scale (1:1056) for Irish towns. From 1840, the six-inch standard was used in Great Britain. The 1:1056 scale was also used for city surveys.
Between 1842 and 1895, about 400 towns were mapped. Scales included 1:500, 1:528, or 1:1056. Other towns were mapped at 1:2500. In 1855, funding was approved for 1:2500 for rural areas and 1:500 for urban areas. The 1:500 scale was called the "sanitary scale." It helped with setting up water and sewer systems.
However, a review in 1892 found that 1:500 maps sold poorly. The government stopped funding their updates. They said any new mapping at this scale had to pay for itself. Very few towns updated their maps. By 1909, only fourteen places had paid for new ones. The review decided that 1:2500 mapping should be updated quickly.
London had very detailed mapping at 1:1056 between 1862 and 1872. This took 326 map sheets. A second version needed 759 sheets due to city growth. This was finished between 1891 and 1895. London was special because land registration became required there in 1900. The OS updated the London maps to help with this.
From 1911 to 1913, Ordnance Survey made larger versions of some 1:2500 maps. They enlarged them to 1:1250. This was for land valuation and tax purposes. The bigger scale gave space for notes. These maps were later replaced by the Ordnance Survey National Grid maps after World War II.
The 20th Century and Beyond
During World War I, Ordnance Survey helped create maps of France and Belgium. In World War II, they made many more maps. These included maps of Antwerp, Brussels, South Africa, Italy, and the Netherlands.
After World War I, Colonel Charles Close helped increase map sales for leisure. He used covers designed by Ellis Martin. In 1920, O. G. S. Crawford became the Archaeology Officer. He used aerial photos to learn more about old sites.
In 1922, Northern Ireland formed its own mapping agency. The Irish Free State also created its own. So, the original Ordnance Survey focused only on Great Britain.
In 1935, a committee reviewed the OS's future. The new Director General, Major-General Malcolm MacLeod, started re-measuring Great Britain. This huge job involved building concrete "trig points" on hilltops. These points were used to make very accurate measurements.
The committee's report guided the Ordnance Survey for the 20th century. The metric national grid reference system was launched. A 1:25000-scale map series was introduced. The one-inch maps were made until the 1970s. Then, they were replaced by the 1:50000-scale series.
The OS headquarters in Southampton was badly damaged in World War II. Staff moved to other buildings. They made maps of Europe for the Normandy invasion. In 1969, a new headquarters was opened in Maybush, Southampton. The old city-centre site is now part of the city's court complex.
The new head office was designed for 4000 staff. It had space for printing maps and storing them. It also had large office areas. The building was known for its concrete mural and special roof.
In 1995, Ordnance Survey finished digitizing its maps. This made the UK the first country with large-scale electronic mapping. By the late 1990s, technology changed things. There was no longer a need for huge map storage areas. The digitizing program replaced the need to print large-scale maps.
In 1990, the Ordnance Survey became an independent agency. In 1999, it became a "trading fund." This meant it had to cover its costs by selling products. It also had to send some profits to the government.
In 2010, OS announced that printing would be done by other companies. This ended over 200 years of in-house printing. A new head office, "Explorer House," opened in Adanac Park in 2011. Prince Philip officially opened it.
In 2015, the organization changed to a government-owned company. It is still fully owned by the UK government. In 2015, a BBC Four TV show called A Very British Map: The Ordnance Survey Story told the history of the OS. In 2023, Ordnance Survey Ltd moved under the new Department for Science, Innovation and Technology.
Types of Maps and Products
The Ordnance Survey creates many paper maps and digital mapping products.
OS MasterMap: The Detailed Digital Map
OS MasterMap is the Ordnance Survey's main digital product. It was launched in 2001. It is a huge database that records every fixed feature in Great Britain. This includes buildings and areas of plants. Each feature has a unique ID number called a TOID. This ID links to a shape that shows the feature's area on the ground.
OS MasterMap comes in different layers:
- Topography: This is the main layer. It shows real-world features like buildings.
- Integrated Transport Network: This layer shows roads and railways. It is used in many satnav systems.
- Imagery: This layer provides aerial photographs.
- Address: This layer adds every address in the UK.
- Address 2: This adds more address details. It includes places with no postal address, like fields.
The Integrated Transport Network was replaced in 2019. The Address layers were removed around 2016. Now, OS MasterMap mainly has Topography and Imagery.
The cost to use OS MasterMap data depends on the area, layers, and time needed. You can use OS MasterMap to create maps for many uses. You can print maps from it that are as detailed as a traditional 1:1250 paper map.
Ordnance Survey says OS MasterMap data is always up-to-date. It is reviewed constantly. This mapping project is very large and detailed. By 2009, it had about 440 million TOIDs. The database was 600 gigabytes in size.
Maps for Businesses
Ordnance Survey makes many products for businesses. These include utility companies and local councils. The data is given on discs or online. Businesses need to buy a license to use this data. Some main products are:
- OS MasterMap: This is the most detailed map. It shows individual buildings.
- OS VectorMap Local: A customizable map at 1:10,000 scale.
- Meridian 2, Strategi: These are mid-scale maps.
- Boundary-Line: This map shows official borders. These include counties and parishes.
- Raster versions of leisure maps: These are digital images of maps at different scales.
Maps for Fun and Leisure
OS publishes many maps for leisure activities:
- Tour (around 1:100,000): These maps cover a county-sized area. They show major roads and tourist information. They have sky-blue covers.
- OS Landranger (1:50,000): This is a general-purpose map. It has pink covers. 204 sheets cover all of Great Britain and the Isle of Man. It shows all footpaths but with less detail than Explorer maps.
- OS Landranger Active (1:50,000): These are waterproof versions of some OS Landranger maps.
- OS Explorer (1:25,000): These maps are for walkers and cyclists. They have orange covers. 403 sheets cover all of Great Britain. These are the most detailed leisure maps. They show all footpaths and countryside details for easy navigation. Some special "OL" sheets cover areas of high interest, like the Lake District. These maps replaced the old Pathfinder maps. Since 2015, new OL series maps come with a mobile download version.
- OS Explorer Active (1:25,000): These are waterproof versions of OS Explorer maps.
- Activity Maps: These are special maps for specific activities. For example, there are map packs for off-road cycling.
Some older map series like Route and Road were stopped in 2010. The Road series was brought back in 2016.
Mobile Apps
In 2013, Ordnance Survey released its first app, OS MapFinder. Since then, they have added more.
- OS Maps: This app is free to download for iOS and Android. Users can access maps on their devices. They can also plan and record routes. Users can subscribe to download high-resolution maps. These maps can be used offline without signal.
- OS Maps Web: This is a web page version of OS Maps. Users can access maps from a web browser. They can plan custom routes and print maps.
- OS Locate: This free app was launched in 2014. It helps users find their exact location quickly. It shows grid reference, latitude, longitude, and altitude. OS Locate works without a mobile signal. It uses the device's built-in GPS.
Custom Maps
Ordnance Survey offers OS Custom Made maps. This service lets you choose the exact area you want mapped. You can get maps at 1:50,000 or 1:25,000 scale. They can be folded or flat. You can also add your own titles and cover images.
They also make more detailed custom maps. These are at 1:1,250 or 1:500 scale. These are made from their large-scale digital data.
Maps for Education
Ordnance Survey provides copies of its maps for schools. These are used in geography lessons in Britain and former British colonies.
In the 2000s, OS gave free OS Explorer Maps to 11-year-olds. Over 6 million maps were given away by 2010. This program was replaced by free access to the Digimap for Schools service.
OS also helps schoolchildren learn about GIS (Geographical Information Systems). They launched "MapZone," a website for kids. It has learning tools and map games. Ordnance Survey publishes a journal called Mapping News for geography teachers.
Other Map Products
Bing Maps uses OS data for its UK maps. Philip's publishes OS data in its road and street atlases. Cassini Publishing Ltd reprints old Ordnance Survey maps. These old maps are made to fit modern grid lines. This means old features line up with modern ones.
Digital maps allow OS to sell maps electronically. Many companies are licensed to sell OS maps on CD/DVD. They also offer them online. Users can view maps on a PC, laptop, or smartphone. They can also print copies. The software often works with GPS. This lets users see their position on the map.
Free Access to Old Maps
The National Library of Scotland offers free access to OS maps from 1840 to 1970. These include maps at various scales. The Society for All British and Irish Road Enthusiasts (SABRE) also has a large archive of OS maps.
Wikimedia has full sets of scans of many old OS maps. These include the First Series one-inch maps of England, Wales, and Scotland. They also have the Seventh Series One-inch maps of Great Britain.
How Maps are Made
The first Ordnance Survey maps were made using triangulation. For the second survey in 1934, this method was used again. This led to building many triangulation pillars (called "trig points"). These are short concrete pillars on hilltops. Their exact locations were found by triangulation. Then, less precise methods filled in the details between them.
Modern Ordnance Survey maps are mostly based on aerial photographs. But many trig points still exist. The Ordnance Survey still has surveyors across Great Britain. They visit and survey areas that cannot be mapped from the air. For example, land hidden by trees. Their goal is to survey major new features within six months.
Today, surveying is easier with Global Navigation Satellite System (GNSS) technology. This allows for very precise measurements. The Ordnance Survey manages a network of GNSS stations called "OS Net." These are used for surveying. Other organizations can also pay to use this network.
The Ordnance Survey maintains special reference points. These link OS map points to modern systems like GPS. Ordnance Survey maps of Great Britain use the Ordnance Survey National Grid for locations. This grid is called OSGB36. It was introduced after the 1936–1953 survey.
For heights, Ordnance Survey uses a system based on Ordnance Datum Newlyn. This is a height reference point. It is based on the average sea level measured in Newlyn, Cornwall, between 1915 and 1921. In 2016, OS updated this reference. This caused a small upward shift of about 25mm. Because of this, Calf Top hill became a mountain.
The OS CartoDesign team is very important. They are in charge of map design. They make sure all new products look good.
Research and Development
For many years, Ordnance Survey has had a research department. They work on different areas of geographical information science, including:
- How people understand maps (spatial cognition).
- Making maps simpler (map generalization).
- Creating models for spatial data.
- Using remote sensing (like satellites) to gather data.
- Understanding the meaning of map data (semantics and ontologies).
Ordnance Survey supports academic research. They work with universities. The research department helps students with their studies. Most OS products are available to UK universities through the Digimap agreement. Data is also shared for research that helps OS's own goals.
More information can be found at Ordnance Survey Research.
Access to Data and Feedback
Ordnance Survey has faced some criticism. People have said that OS has a monopoly on geographic data in the UK. Even though it's a government agency, it had to act like a business from 1999 to 2015. This meant it had to fund itself by selling its data.
In 1987, a report called the Chorley Report suggested making geographic information more available. It said this was important for the UK.
In 2007, OS was criticized for hiring a company to understand the "free data movement." This company looked into which politicians supported OS's policies.
OS OpenData: Free Access to Maps
The government decided to release some Ordnance Survey data sets for free. This was in response to public feedback. On April 1, 2010, Ordnance Survey launched OS OpenData. This data could be used and shared freely.
Some people were disappointed that more detailed maps, like the 1:50,000 and 1:25,000 leisure maps, were not included. OS argued that if users didn't pay, the government would have to pay £30 million a year to collect new map data.
In 2018, more parts of OS MasterMap were released for free. These included:
- Property boundaries from OS MasterMap Topography Layer.
- TOIDs from OS MasterMap Topography Layer, added to OpenMap Local.
Other data became free for small businesses. This included:
- OS MasterMap Topography Layer (with building heights).
- OS MasterMap Greenspace Layer.
- OS MasterMap Highways Network.
- OS MasterMap Water Network Layer.
- OS Detailed Path Network.
These are available through special online tools on the OS Data Hub.
Old Maps for Everyone
Old Ordnance Survey maps are generally available. This is because they are covered by Crown Copyright. Works older than fifty years are free to use. This includes old surveys of Britain and Ireland. However, finding good original copies can be hard. Ordnance Survey does not provide old maps for free. Instead, they partner with companies to sell improved copies.
The National Library of Scotland makes old Ordnance Survey maps of Great Britain available online. The Society for All British and Irish Road Enthusiasts (SABRE) also has a large online collection of old OS maps.
Wikimedia has full sets of scans of many old OS maps. These include the one-inch maps of England, Wales, and Scotland. They also have the Seventh Series One-inch maps of Great Britain.
Images for kids
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Grid square TF from the Ordnance Survey National Grid, shown at a scale of 1:250,000. The map shows the Wash and the North Sea, as well as places within the counties of Lincolnshire, Cambridgeshire and Norfolk
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Part of an Ordnance Survey map, at the scale of one inch to the mile, from a New Popular Edition map published in 1946
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Pollokshaws on Roy's Military Survey of Scotland (1747–1755)
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The original draftsman's drawings for the area around St Columb Major in Cornwall, made in 1810.
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Detail from 1901 Ordnance Survey map of the Imperial fortress colony of Bermuda (showing St. George's Town and St. George's Garrison), compiled from surveys carried out between 1897 and 1899 by Lieutenant Arthur Johnson Savage, Royal Engineers.
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The former headquarters of the Ordnance Survey in London Road, Southampton (2005).
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The cover of the 5th series OS map Chelmsford and Southend sheet 108. Art by Ellis Martin
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Front cover of a one-inch to the mile New Popular Edition, from 1945
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Detailed scan of a complete 7th series sheet
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Former Ordnance Survey headquarters in Maybush, Southampton, used from 1969 until 2011
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Headquarters in Adanac Park opened in 2011
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Ordnance Survey maps on sale
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Illustration of the Ordnance Survey National Grid coordinate system, with Royal Observatory Greenwich as an example
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The Ordnance Survey maps of Great Britain use the Ordnance Survey National Grid
- Admiralty chart
- Benchmark (surveying)
- Cartography
- Directors of the Ordnance Survey
- Geoinformatics
- Grid reference
- Great Trigonometric Survey
- Irish national grid reference system
- Ordnance Survey National Grid
- Hydrography
- Hydrographic survey
- United Kingdom Hydrographic Office
- International Map of the World
- Geographers' A-Z Map Company, principal partner of the OS
- Martin Hotine, founder of the Directorate of Overseas Surveys
- (List of) national mapping agencies
- Ordnance datum (sea level)
- Ordnance Survey International
- Ordnance Survey Ireland
- Ordnance Survey of Northern Ireland
- Romer, a device for accurate reading of grid references from a map
- Napoleonic Cadastre
