Ordnance Survey

Image produced from the Ordnance Survey Get-a-map service. Image reproduced with kind permission of Ordnance Survey and Ordnance Survey of Northern Ireland.

A 1:50,000 map of [[Shepshed

in Leicestershire]]Ordnance Survey (OS) is an executive agency of the United Kingdom government. It is the national mapping agency for Great Britain Note that the Ordnance Survey currently deals only with maps of Great Britain (and to an extent, the Isle of Man). Northern Ireland, whilst an integral part of the United Kingdom, is mapped by a separate government agency, the Ordnance Survey of Northern Ireland., and one of the world's largest producers of maps.

Origins

The roots of Great Britain's Ordnance Survey (OS) go back to 1747, when King George II commissioned a military survey of the Scottish highlands following the Jacobite revolt of 1745. William Roy was the engineer responsible for this pioneering work; one of the staff involved was noted artist Paul Sandby. It was not until 1790 that the Board of Ordnance (the predecessor of the Ministry of Defence) began a national military survey starting with the south coast of England in anticipation of a French invasion.

By 1791, the Board had purchased the new Ramsden theodolite, and work commenced on mapping southern Great Britain using a baseline that Roy himself had previously measured and which crosses the present Heathrow Airport. A set of postage stamps featuring maps of the Kentish village of Hamstreet was issued in 1991 to mark the bicentenary.

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

During the next twenty years approximately one-third of England and Wales was mapped at the same scale. (see Principal Triangulation of Great Britain.) It was gruelling work: Major Thomas Colby, later the longest serving Director General of the Ordnance Survey, walked 586 miles in 22 days on a reconnaissance in 1819. In 1824, Colby and most of his staff moved to Ireland to work on a six-inch to the mile (1:10,560) valuation survey. 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. He 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.

After the first Irish maps began to come out in the mid-1830s, the Tithe Commutation Act led to calls for similar six-inch surveys in England and Wales. After official prevarication, the development of the railways added to pressure that resulted in the 1841 Ordnance Survey Act. 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 OS was in disarray for several years with arguments about which scales to use. Major-General Sir Henry James was now Director General, and he saw how photography could be used to make maps of various scales cheaply and easily.

Due to the fire, the OS relocated to a site in Southampton, and the twenty-five inch to the mile survey was complete by 1895. Despite heavy bomb damage in World War II, the OS has remained in Southampton since 1969.

The 20th century

The old site of the OS in Southampton city centre, as seen today.

During the First World War the OS was more involved in preparing maps of France and Belgium for its own use. Many more maps were created during World War II, including :
* 1:40,000 map of Antwerp, Belgium
* 1:100,000 map of Brussels, Belgium
* 1:5,000,000 map of South Africa
* 1:250,000 map of Italy
* 1:50,000 map of Northeast France
* 1:30,000 map of the Netherlands with manuscript outline of German Army occupation districts

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

The Davidson Committee was established in 1935 to review the Ordnance Survey's future. The new Director General, Major-General Malcolm MacLeod, started the retriangulation of Great Britain, an immense task which involved erecting concrete triangulation pillars (trig points) on prominent (often inaccessible) hilltops throughout Great Britain. These were intended to be infallibly constant positions for the theodolites during the many angle measurements, which were each repeated no less than 32 times.

The Davidson Committee's final report set the OS on course for the twentieth century. The national grid reference system was launched, with the metre as its measurement. An experimental new 1:25,000 scale map was introduced. The one-inch maps remained for almost forty years before being superseded by the 1:50,000 scale series, as proposed by William Roy more than two centuries earlier.

The OS had outgrown its site in the centre of Southampton (made worse by the bomb damage of the Second World War), and in 1969 moved to a site in the suburb of Maybush, towards the edge of the city, where it remains today. Some of the remaining buildings of the original city centre site are now used as part of the court complex. In 1995 the Ordnance Survey digitised the last of about 230,000 maps, making the United Kingdom the first country in the world to complete a programme of large-scale electronic mapping. The OS is now a civilian organisation with executive agency status.

UK Map Range

Ordnance Survey maps are available in most bookshops, in a variety of scales:
* Route (1:625,000) - Designed for long-distance road users. One double-sided map (dark blue cover) covers the whole of Great Britain.
* Road (1:250,000) - Designed for road users. They have green covers; 8 sheets cover the whole of Great Britain.
* Landranger (1:50,000) - The "general purpose" map. They have pink covers; 204 sheets cover the whole of Great Britain and the Isle of Man.
* Explorer (1:25,000) - Specifically designed for walkers and cyclists. They have orange covers; 403 sheets cover the whole of Great Britain (the Isle of Man is excluded from this series). Explorer maps have replaced two older series of 1:25,000 map:
** Outdoor Leisure - Also for walkers and cyclists. These 33 maps specifically covered tourist destinations. Identified by their yellow covers and often double-sided, they predated the Explorer maps. They covered a larger area than Pathfinders.
** Pathfinder - Pathfinders, with their green covers, were the predecessors to the Explorer series. These maps were smaller than the new ones and generally had no overlap between adjacent sheets. There were over 1,300 maps in the series. Some Pathfinders were phased out by the arrival of Outdoor Leisure maps, the remainder being later replaced by the new Explorer series.

Also produced are various historical and archaeological maps, and road maps of certain popular "tourist" areas, all at a variety of scales. The Ordnance Survey produces a free mapping index, showing which parts of the country are covered by which maps. The Ordnance Survey also produces more detailed mapping at 1:10,000 and 1:1,250 scales, which is available from some of the more specialist outlets. This is produced to order from digital data, so the customer can choose exactly which area the map should cover.

Cartography

The Ordnance Survey maps of Great Britain use the British national grid reference system

The original maps were made by triangulation. For the second survey, in 1935, this process was also used, and resulted in the building of many triangulation pillars (trig points): short (approx 4 feet/1.2 m high), usually square, concrete or stone pillars at prominent locations such as hill tops. Their precise locations were determined by triangulation, and the details in between were then filled in with less precise methods. Modern Ordnance Survey maps are based on aerial photographs, but large numbers of the pillars remain.

The OS still maintains a set of master geodetic reference points to tie the OS geographic datums to modern measurement systems including GPS. The Ordnance Survey maps of Great Britain do not use latitude and longitude to indicate position but a special grid. The grid is technically known as OSGB36 ™ (Ordnance Survey Great Britain 1936), and was introduced after the retriangulation of 1936–53.

OS MasterMap

The Ordnance Survey's flagship digital product, launched in November 2001, is OS MasterMap. This is a database that records every fixed feature of Great Britain larger than a few metres in one continuous digital map. Every feature is given a unique TOID (topographical identifier), a simple identifier that includes no semantic information. Typically each TOID is associated with a polygon that represents the area on the ground that the feature covers, in National Grid coordinates. MasterMap is offered in themed "layers", for example, a road layer and a building layer, each linked to a number of TOIDs. Pricing of licenses to MasterMap data depends on the total area requested, the layers licensed, the number of TOIDs in the layers, and the period in years of the data usage.

MasterMap can be used to generate maps for a vast array of purposes. Although the scale on a digital map is much more flexible than a paper map, one can print out maps from MasterMap data with detail equivalent to a traditional 1:1250 paper map.

The OS claims that MasterMap data is never more than 6 months out of date, thanks to continuous review. The scale and detail of this mapping project is so far unique. Around 440 million TOIDs have so far been assigned, and the database stands at 600 gigabytes in size. MasterMap is currently (August 2005) at version 6.

The OS is encouraging users of its old OS Landline data to migrate to MasterMap.

Geographical Information Science Research at Ordnance Survey

Since about 2001 Ordnance Survey has had a very active Research & Innovation department that is active in several areas of Geographical information Science including:
* Spatial cognition
* Map Generalisation
* Spatial Data Modelling
* Remote sensing and analysis of remotely sensed data
* Semantics and ontologies

Ordnance Survey actively supports the academic research community through its External Research and University Liaison team. The R&I department actively support MSc and PhD students as well as engaging in colloborative research. Most Ordnance Survey products are available to UK Universities that have signed up to the DigiMap agreement and data is also made available for research purposes that advances Ordnance Survey's own research agenda.

More information can be found at Research & Innovation

References

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External links

* Ordnance Survey
* [1] detailed mapping required by law for planning application/developments in the UK
*old-maps.co.uk 19th century Ordnance Survey maps of the whole of Great Britain
* 19th century Ordnance Survey maps of Lancashire
* National GPS network information: A guide to coordinate systems in Great Britain
* OS MasterMap official site
* The Guardian: Devil is in the detail as OS maps out the future by Paul Brown, March 8, 2004
* CADserver: AEC Feature: Master and servant, Nov/Dec 2004
*Royal Engineers Museum - Survey -origins of the Ordnance Survey
*Royal Engineers Museum - General Roy -Biography
*[2] History of Ordnance Survey

Ordnance Survey: Encyclopedia BETA

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