Retriangulation of Great Britain

The Retriangulation of Great Britain was a triangulation project carried out between 1935 and 1962 that sought to improve the accuracy of maps of Great Britain. Data gathered from the retriangulation replaced data gathered during the Principal Triangulation of Great Britain, which had been performed between 1783 and 1851.

The work was designed to form a complete new survey control network for the whole country, and to unify the mapping of the United Kingdom from local county projections into a single national datum projection and reference system. Its completion led to the establishment of the OSGB36 datum and Ordnance Survey National Grid in use today.