Ordnance Survey
The national mapping agency of Great Britain and a government-owned provider of geospatial data, mapping and location services.
Last updated August 21, 2026
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Overview
Ordnance Survey (OS) is the national mapping agency of Great Britain and one of the United Kingdom’s principal providers of authoritative geographic information. Its origins lie in the military and security requirements of the eighteenth century. After the Jacobite rising of 1745, British authorities recognised the need for reliable maps of the Scottish Highlands. The possibility of invasion during the Napoleonic Wars added a broader national-security rationale for systematic surveying. Work began under the Board of Ordnance, with early contributions from surveyors including William Roy, and developed into a national programme of triangulation and topographic mapping. The organisation’s historical importance extends beyond military cartography. During the nineteenth century it produced increasingly detailed maps for land administration, taxation, valuation, infrastructure, urban planning and public works. Surveys of Ireland helped establish detailed large-scale mapping methods, while the County Series provided comprehensive coverage of Great Britain at scales suited to professional and administrative use. Ordnance Survey also developed specialist cartographic and reproduction techniques, including photozincography, and contributed to the preservation and publication of important historical map and manuscript facsimiles. The agency’s best-known public products include the Explorer leisure map series at 1:25,000, the Landranger series at 1:50,000 and a range of smaller-scale road and regional maps. Its professional and institutional portfolio is more extensive than its paper-map reputation suggests. OS supplies detailed digital mapping, address and property-related information, topographic databases, APIs, online route-planning tools, mobile applications and location-based services. Large-scale mapping, including data associated with OS MasterMap, supports land management, planning, utilities, transport, emergency response, construction, environmental analysis and public administration. Consumer services such as OS Maps provide route planning, navigation, discovery and sharing features for outdoor activities. Paper maps now represent only a small proportion of the organisation’s revenue, while digital data, licensing, online services and geospatial products form the core of its modern business. Ordnance Survey data is used by central and local government, commercial organisations, developers, infrastructure operators, researchers and the public. Its authority derives from national coverage, consistent surveying standards, maintained geographic databases and a long institutional record. Since 1 April 2015, the organisation has operated as Ordnance Survey Ltd, a company wholly owned by the UK public sector. It remains accountable to the UK government, with its board responsible to the Secretary of State for Science, Innovation and Technology. Although its principal geographic remit is Great Britain, its data, technical expertise and mapping products have wider relevance to international geospatial practice. The brand therefore combines the authority of a national public institution with the operating model of a modern digital geospatial company.
History
Ordnance Survey developed from Britain’s military surveying needs in the aftermath of the Jacobite rising of 1745. Lieutenant-Colonel David Watson proposed a systematic survey of the Scottish Highlands, and William Roy became one of the key figures in establishing the technical standards and methods that later shaped the organisation. The prospect of invasion during the Napoleonic period encouraged the Board of Ordnance to extend surveying beyond Scotland and begin a national military mapping programme. The national survey began in earnest around 1790, using improved instruments and a measured baseline on Hounslow Heath. In 1801 the first one-inch-to-the-mile map was published, covering Kent, followed soon afterward by mapping of Essex. Surveying proceeded unevenly because of military priorities, but by the middle of the nineteenth century much of England and Wales had been covered at the one-inch scale. The Principal Triangulation of Great Britain, associated with Roy, William Mudge, William Yolland and later Alexander Ross Clarke, created a framework for consistent national mapping. Major Thomas Colby directed the organisation for many years and oversaw the detailed survey of Ireland. The Irish work helped establish six-inch mapping and introduced systematic methods for recording place names. It also demonstrated the value of detailed maps for valuation and administration. The Ordnance Survey later applied comparable approaches in Great Britain, producing the County Series at six-inch and twenty-five-inch scales. Detailed urban surveys were also undertaken, with especially extensive mapping of London. In the nineteenth century, Ordnance Survey mapping supported taxation, land valuation, infrastructure, sanitation, engineering and public administration in addition to defence. The organisation experimented with reproduction technology, and photozincography enabled maps and historic documents to be reproduced more efficiently. The Ordnance Geological Survey, founded in 1835, remained associated with the Ordnance Survey until the twentieth century before becoming the British Geological Survey. The organisation moved its headquarters to Southampton after a fire at the Tower of London in 1841. Administrative responsibility changed over time: after the Board of Ordnance was abolished in 1855, the Survey was placed under the War Office and later transferred to the Office of Works. During the First and Second World Wars it produced mapping for military operations in Britain and overseas theatres, including parts of continental Europe and other regions. After the Second World War, the older County Series was progressively superseded by mapping based on the Ordnance Survey National Grid. This provided a standard national reference system for large-scale topographic mapping and became fundamental to British surveying, planning and geographic information systems. During the late twentieth and early twenty-first centuries, OS converted much of its mapping into digital databases and developed products for public authorities, commercial users and consumers. The modern organisation combines national mapping responsibilities with commercial delivery of licensed data, APIs, digital services and consumer applications. Paper maps remain an important public-facing part of the brand, particularly the Explorer and Landranger series, but they represent only a small share of annual revenue. On 1 April 2015, Ordnance Survey adopted the corporate form Ordnance Survey Ltd while remaining wholly government-owned. Its board continues to be accountable to the relevant Secretary of State, and its principal role remains the creation and maintenance of authoritative geographic information for Great Britain.
- 2015
Ordnance Survey Ltd established
[1]The organisation began operating as a government-owned company, Ordnance Survey Ltd, while remaining in full public ownership.
- 1891
One-inch mapping of Great Britain completed
[1]The first complete one-inch-to-the-mile series for Great Britain was published.
- 1858
Principal Triangulation improved
[1]Alexander Ross Clarke completed a new geodetic survey based on the Airy spheroid, strengthening the mathematical framework of national mapping.
- 1841
Headquarters move to Southampton
[1]Following a fire at the Tower of London, the organisation relocated its headquarters to Southampton.
- 1841
Ordnance Survey Act
[1]Legislation provided surveyors with authority to enter property for surveying purposes and helped support systematic mapping in Great Britain.
- 1835
Geological surveying becomes associated with OS
[1]The Ordnance Geological Survey was founded and remained a branch of the Ordnance Survey until 1965.
- 1824
Detailed survey of Ireland begins
[1]Under Thomas Colby, the Survey undertook a detailed six-inch-to-the-mile survey of Ireland for valuation and administrative purposes.
- 1801
First one-inch map published
[1]The first one-inch-to-the-mile Ordnance Survey map, covering Kent, was published, followed by mapping of Essex.
- 1790
National military survey begins
[1]The Board of Ordnance began systematic surveying of Great Britain, building on William Roy’s earlier work and using improved geodetic instruments.
- 1747
Proposal for a Highland survey
[1]David Watson proposed a military survey of the Scottish Highlands after the Jacobite rising, establishing an important foundation for the later national mapping organisation.
Products and positioning
A trusted national authority for accurate, maintained and detailed geographic information, serving government, businesses, institutions and outdoor consumers.
Professional geospatial data
OS MasterMap
A detailed digital mapping and geographic data product used by government, infrastructure operators, businesses, planners and other professional users. It supports analysis of features, land, buildings, transport networks and addresses, and is designed for integration into geographic information systems and operational workflows.
Consumer digital service
OS Maps
A digital mapping and outdoor activity service that provides access to Ordnance Survey mapping, route planning, navigation and route-sharing tools. It extends the traditional paper-map experience to web and mobile users and is aimed particularly at walking, cycling and other outdoor activities.
Leisure paper maps
Explorer
The 1:25,000 Explorer series provides detailed coverage designed for walking, hiking, cycling and other outdoor recreation. Its scale shows paths, terrain and local features in substantial detail and makes it one of the organisation’s principal consumer map ranges.
Leisure paper maps
Landranger
The 1:50,000 Landranger series offers broader regional coverage for route planning, touring, walking and general geographic reference. It balances area coverage with enough detail for many recreational and travel uses.
National geospatial database
National Geographic Database
The organisation’s maintained digital geographic information resources underpin mapping and location services across Great Britain. The data supports national coverage, consistent reference systems and the creation of products for public-sector, commercial and consumer users.
Brand decisions
2015
Adoption of the Ordnance Survey Ltd corporate structureStrategyBackground
The national mapping agency was reorganised to operate as a company while retaining full public ownership and government accountability.
Action taken
From 1 April 2015, Ordnance Survey operated as Ordnance Survey Ltd, with its board remaining accountable to the responsible Secretary of State.
Aftermath
The change preserved the organisation’s public ownership while giving it a corporate operating structure for its mapping, data and location-services activities.
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