Catalogue description Ordnance Survey of Great Britain: Six-Inch Maps: National Grid

Between 1948 and 1957, a new edition of the six-inch (1:10,560) map began to be issued 'on National Sheet Lines'.

A Provisional Edition of the 1:10,560 map on National Grid sheetlines was introduced in 1953. This map was designed to provide, as quickly as possible, an up-to-date map from the best available information. The sheets were produced by fitting the material of the County Series sheets, together with revision data, into the framework of the National Grid, with a minimum amount of redrawing. As far as possible, the Provisional Edition incorporated revision undertaken between 1948 and 1957 at the 1:10,560 scale for the preparation of the Seventh Series one-inch (1:63,360) map.

The Provisional Edition was not intended to be a definitive publication. On publication of the Regular Series sheets, the corresponding Provisional Edition sheets were withdrawn. This series, however, contains a large number of Provisional Edition sheets: these are indicated in the catalogue.

It was originally intended that each sheet would represent a quadrant of a 10-kilometre square of the National Grid and so depict an area 5 x 5 kilometres. However, some sheets have an extended layout, especially where, as in coastal areas, this avoided the creation of sheets with large blank areas.

National Grid lines are shown at one-kilometre intervals. Full grid values are given at the corners of each sheet, and the intervening values in kilometres, by the last two figures of the kilometre values from 00 to 99 inclusive. An inner border is divided at 100-kilometre intervals. All sheets also show latitude and longitude in association with the inner border; abbreviated values are given at 1-minute intervals and full values, in degrees and minutes, accompanying the 1-minute interval nearest to the sheet corners.

Outer borders are graduated in scales of feet (west), yards (south), furlongs (east), and links and chains (north). A note on the relationship between true, magnetic, and grid north appears in the south margin of the sheet, together with an explanation of how to give a National Grid reference correct to 100 metres, two panels of conventional signs, an index diagram to adjoining sheets, a 'survey diagram' where appropriate, giving the dates of survey of component larger scale sheets and, beneath, revision notes on other information on the map.

The numbering of National Grid maps derives from the numbering of sheets of the1:25,000 map, each of which is based on a ten-kilometre square. Each sheet of the National Grid 1:10,560 map, with sides representing five kilometres, depicts a quarter of the area shown on a 1:25,000 sheet. The number of each 1:10,560 sheet is linked to the number of its 'parent' 1:25,000 sheet: for example, if the 1:25,000 sheet number were TQ 47, the 1:10,560 sheet relating to its north-east quadrant would be TQ 47 NE. More detailed indexes are provided by the 1:63,360 sheets, on which each 10-kilometre grid line is emphasized, and by the 1:625,000 maps which are also gridded at 10-kilometre intervals.