Retriangulation Of Great Britain
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__NOTOC__ The retriangulation of Great Britain was a
triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle ...
project carried out between 1935 and 1962 that sought to improve the accuracy of maps made of
Great Britain Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
. Data gathered from the retriangulation replaced data gathered during the
Principal Triangulation of Great Britain The Principal Triangulation of Britain was the first high-precision triangulation survey of the whole of Great Britain (including Ireland), carried out between 1791 and 1853 under the auspices of the Board of Ordnance. The aim of the survey was t ...
, which had been performed between 1783 and 1851.


History

The retriangulation was begun in 1935 by the Director General of the
Ordnance Survey Ordnance Survey (OS) is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of 1745. There was ...
, Major-General Malcolm MacLeod. It was directed by the cartographer and mathematician Martin Hotine, head of the Trigonometrical and Levelling Division. A problem during the Principal Triangulation was that the exact locations of surveying stations were not always rediscoverable, relying on buried markers and unreliable local knowledge. To overcome this, a network of permanent surveying stations was built, most familiarly the concrete triangulation pillars (about 6,500 of them) found on many British Isles hill and mountain tops, but there were many other kinds of surveying stations used. To minimise differences between the 1783-1851 survey and the retriangulation, eleven Principal Triangulation stations from Dunnose on the
Isle of Wight The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...
to
Great Whernside Great Whernside is a fell in the Yorkshire Dales, England, not to be confused with Whernside, some to the west. Its summit is the highest point of the eastern flank of Wharfedale above Kettlewell. Great Whernside forms the watershed between W ...
in Yorkshire were chosen and pillars erected on them to act as the core framework from which all other measurements were made. The main work of the Retriangulation was finished in 1962, creating the now familiar
Ordnance Survey National Grid The Ordnance Survey National Grid reference system (OSGB) (also known as British National Grid (BNG)) is a system of geographic grid references used in Great Britain, distinct from latitude and longitude. The Ordnance Survey (OS) devised the ...
, with the system continuing to be used and measurements refined by ground-based surveying into the 1980s, after which satellite use took over. Electronic measuring devices were introduced towards the end of the Retriangulation, but at that time were not proven reliable enough to replace traditional surveying.


Notes and references


Bibliography

* * *{{cite book , year=1980 , editor-first=W. A. , editor-last=Seymour , title=A History of the Ordnance Survey , publisher=Dawson , location=Folkestone, England , isbn= 0-7129-0979-6 , url=https://books.google.com/books?id=PWkKAQAAIAAJ , oclc=654935343 , postscript = . Freely available online at th
Ordnance Survey, Seymour


See also

*
Geodesy Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), Earth rotation, orientation in space, and Earth's gravity, gravity. The field also incorporates studies of how these properti ...
*
OSGB36 The Ordnance Survey National Grid reference system (OSGB) (also known as British National Grid (BNG)) is a system of geographic grid references used in Great Britain, distinct from latitude and longitude. The Ordnance Survey (OS) devised the ...
*
Reference frame In physics and astronomy, a frame of reference (or reference frame) is an abstract coordinate system whose origin (mathematics), origin, orientation (geometry), orientation, and scale (geometry), scale are specified by a set of reference point ...
*
Triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle ...
*
Trig point A triangulation station, also known as a trigonometrical point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity. The nomenclature varies regionally: they ...


External links


Daily Telegraph article about the retriangulation of Great BritainNational GPS NetworkInformation and Maps on many aspects of Trigangulation (& Levelling) in Great Britain
Angle Surveying of the United Kingdom Geography of Great Britain Geodetic surveys