Levelling Homepage Ordnance Survey's
Levelling
of Great Britain
[1GL, 2GL Abstract]
[1GL, 2GL Transcription]
[Timeline]
[FBM List]
TrigTools

Timeline

Show: Levelling TriangulationGeneralMapsorMaps2Charles Close
Hide:IrelandIreland England&WalesEnglandWales ScotlandScotland

[assume Great Britain unless specifed]
1800's1900's2000's
First primary levelling (+)
1840  1860
original levelling - Ireland
1840  1850
Ireland
subsequent levelling - Ireland
  1890
Ireland
Second geodetic levelling - England & Wales (+)
1912  1921
EnglandWales
(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
Scotland
(2nd World War)
1939  1945
Second geodetic levelling - East Anglia and Kent
1946  1951
Third geodetic levelling - England & Wales
1950  1968
EnglandWales
Third geodetic levelling - Scotland
1956  1968
Scotland
Cyclic relevelling - England & Wales
1956  1989
EnglandWales
Cyclic relevelling - Scotland
1959  1989
Scotland
GPS era
1989  now
[assume Great Britain unless specifed]
1800's1900's2000's

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

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