This series consists of Object Name Book (ONB) folders containing information relating to the names of objects depicted on Ordnance Survey mapping of England and Wales, together with the authority for their spelling. Their primary purpose is to list and define the location and extent of named objects and area features. The 'objects' named are both natural and man-made, and include streams, rivers and hills; roads, railways and canals; domestic, public and industrial buildings, and antiquities. In addition, they also contain technical detail (levelling and control information), as well as the survey history of the mapping sheet to which they refer.
These ONBs relate to the National Grid Series mapping which was created in the period after the Second World War in accordance with the recommendations of the Davidson Committee.
For the first time all OS mapping was re-cast on national instead of county sheet lines, and on a new national projection which covered the whole country. All scales were superimposed with a National Grid (based on the metre rather than the yard), so providing a single referencing system for all Ordnance Survey map detail. Three 'basic' or largest survey scales were established for which mapping was kept up-to-date by a system of continuous revision: the existing 1:2500 scale was retained for rural areas, a new 1:1250 series was created for the increasingly congested urban area mapping and the 1:10,560 scale retained for mountain and moorland. Most other mapping was derived from the detail of these basic survey scales.
In 1969 a metrication programme replaced the 1:10,560 and 1:63,360 scales with 1:10,000 and 1:50,000 respectively and altitudes and contours at all scales were shown in metric measure.
There are three sets of ONB each relating to different mapping scales:
(a) large-scale urban mapping at 1:1250 (50.688 inches to one mile) scale begun in 1943 and covering all urban areas with at least 20,000 inhabitants; and rural mapping at 1:2500 (25.344 inches to one mile) scale begun in 1948 and re-cast from the old County Series mapping by fitting the old mapping to the new National Grid and projection, eliminating errors, updating and redrawing. After 1973 no revised 1:2500 scale sheets were published for areas covered by the 1:1250 scale. Both scales were placed under continuous revision as each sheet was completed.
(b) large-scale mountain and moorland area mapping at 1:10,560 (6 inches to one mile) scale, begun in 1947 as the Provisional Edition and incorporating revision collected for the Seventh Series 1:63,360 (one inch to one mile) scale; subsequently including the Regular Edition derived from the National Grid series at 1:1250 and 1:2500 scales and in turn used (from 1961) for the medium scale 1:25,000 (2.5 inches to one mile) National Grid Series.
(c) small scale topographical mapping First and Second Series 1:50,000 (1.2672 inches to one mile) scale, which replaced the Seventh Series from 1974 and was renamed the Landranger Series in 1979. The Seventh Series, authorised in 1947, was a completely new edition of the 1:63,360 (one-inch) mapping based on field revision at 1:10,560 (6-inch) scale. The Series was completed in 1961 and thereafter was subject to a cyclical revision based on likely quantity of change. Names were derived from the large-scale 1:10,560 (6-inch) mapping except where they had changed position or status, were new, or were added to define large (over 50 square kilometre) tracts of land. Any field sheet histories enclosed within these ONBs will therefore relate to the 1:10,560 mapping and not the 1:50,000.