Catalogue description Ordnance Survey: Trigonometrical and Levelling Divisions: Levelling Maps and Diagrams

Records from the Primary, Second and Third Levelling of Great Britain by the Ordnance Survey.

These are the levelling route maps, the primary means of reference to the levelling abstracts (OS 54). They are one-inch OS maps and extracts from the six-inch OS series annotated to show the alignment of levelling lines relating to the Primary and Second Geodetic Levelling prior to 1952. The six-inch extracts cover the urban areas which are indicated on the one-inch maps by simple boxed outlines.

Also included in the series are master diagrams of levelling blocks (polygons) showing additional levelling detail and renumbering of existing levelling lines for the Third Geodetic Levelling of 1951-1956. The diagrams cover both scales but do not include the base map detail since they were intended as overlays to the original one-inch and six-inch maps.

The series also includes two sets of bound volumes containing the levelling progress and adjustment maps. These are county maps providing an index to the A and M abstract series (OS 54) and showing the progress of the levelling in Great Britain from the 1950s to 1988, or recording the adjustments made between the Liverpool and Newlyn datum levelling for the whole of Great Britain.

See also OS 54

Ordnance Survey of Great Britain, Directorate of Field Survey, 1946-1973

Ordnance Survey of Great Britain, Field Surveys Directorate, 1974-1978

Ordnance Survey of Great Britain, Surveys and Production Directorate, 1979-1993

From 2007 Ordnance Survey