Ordnance Survey's Levelling of Great Britain

[1GL, 2GL Abstract] [1GL, 2GL Transcription]

[Timeline] [FBM List]

Timeline

Show:	Levelling	Triangulation	General	Maps	or	Maps2	Charles Close

Hide:	Ireland	England&Wales	Scotland

[assume Great Britain unless specifed]	1800's 1900's 2000's
First primary levelling (+)	1840   1860
original levelling - Ireland	1840   1850
subsequent levelling - Ireland	1890
Second geodetic levelling - England & Wales (+)	1912   1921
(World War One)	1914   1918
Measurement of the Ordnance Datum Newlyn	1915   1921
Relevelling of Greater London	1931   1934
Second geodetic levelling - Scotland	1936   1952
(2nd World War)	1939   1945
Second geodetic levelling - East Anglia and Kent	1946   1951
Third geodetic levelling - England & Wales	1950   1968
Third geodetic levelling - Scotland	1956   1968
Cyclic relevelling - England & Wales	1956   1989
Cyclic relevelling - Scotland	1959   1989
GPS era	1989   now
[assume Great Britain unless specifed]	1800's 1900's 2000's

Sources used on this page
Ordnance Survay Maps a descriptive manual - J B Harley
[www.osni.gov.uk]

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