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Large Scale Ordnance Survey maps of Great Britain

Large scale Ordnance Survey mapping was begun in the mid-19th century and the way that it is organised has changed enormously over the years. 

Until the Second World War, individual counties were surveyed separately. Each county had its own sheet numbering and revision and updating was done by county. After the War this changed and sheet numbering was based on the National Grid system, one system covering the whole of Great Britain. Because of this change, the County Series and National Grid Series maps have to be referred to, and ordered, quite separately. This page deals with the three largest scales of Ordnance Survey mapping available: the 1:10000, 1:2500 and 1:1250 scales as well as the OS Town Plans at 1:500 scale.

1. Modern large scale maps: National Grid Series (Post-World War II)

The National Grid mapping covers the whole of mainland Britain but not Northern Ireland or the Irish Republic. It was begun after World War II, and is still going on today.

1.1 The different scales

The 1:10 000 (c. 6 inches to I mile) scale covers the whole of Great Britain and is the largest scale National Grid series to cover mountain and moorland areas and to show contours. Some of the earlier editions are the imperial scale of 1:10,560 (exactly 6 inches to 1 mile). There are sometimes more frequent editions of the 1:10 000 scale than of the larger scales.

The 1:2500 (c. 25 inches to one mile) scale does not cover remote mountain and moorland areas. The 1:1250 scale covers only urban areas. If an area is covered at 1:1250 (c.50 inches to 1 mile) scale no current 1:2500 will be available as the 1:2500 was superseded by the 1:1250 in urban areas, usually in the 1970s. Before then both scales could cover the same area. It is therefore essential to order both scales in 1:1250 areas to make sure of obtaining all editions. There are usually more frequent and recent editions for urban areas where more changes have occurred.

For samples of the various scales please see the display on the wall in the catalogue area of the Maps Reading Room. It should be remembered that the largest scale maps cover the smallest area, so the more detail you have, the more sheets you will need.

1.2 Finding the right sheet

To order a National Grid sheet, you need to have an OS National Grid reference. There are various ways to find this. If you have a placename or postcode go to Get-a-Map on the OS web site to obtain one.

If you don't have a precise place name or are looking at a wider area rather than a specific point, you will probably find it easier to use a graphic index, which shows the area covered by each sheet. There are graphic indexes for the 1:2500 scale maps in the drawers on the left hand side of the catalogue area for all of Great Britain; in addition there are indexes, arranged by county, for England and Wales which show both the National Grid and the sheetlines for the older County Series maps

1.3 Editions

Owing to the large number of sheets and variety of edition dates there is no list of editions available; all available editions of whichever sheet you order will be delivered. There will generally be more frequent editions for urban than for rural areas.

1.4 Ordering

Most editions of the 1:2500 and 1:1250 scale maps, and all editions of the 1:10 000 scale, are on paper sheets and are stored in the basement. They have to be ordered using the ABRS. Some of the most recent 1:2500 and 1:1250 scale maps are on microfilm/fiche and are on open access. The most recent digital maps can be accessed from the OS data terminal.

1.5 Microform

Recent editions of the 1:2500 and 1:1250 sheets are usually held on microfilm aperture cards. These are on open access in the Maps Reading Room, in the white cabinets next to the Reference Enquiry Desk, filed in order of the National Grid letter prefix then number. They can be consulted on most of the microfiche readers; the original scale can be obtained on reader-printers no.10 or no.14.

1.6 OS Digital data

The Ordnance Survey phased out production of 1:2500 paper mapping (although prints from the digital mapping can still be provided) in the early to mid 1990s and the 1:10000 followed suit. Since 1997 the library has received all the large scale mapping in a digital format of which a "snapshot" is received each year. You can view this data easily in the maps reading room on a special terminal, and make print-outs subject to the terms and conditions imposed by OS.To find your area you need either an OS national grid reference or a place name. The grid reference can either be found from the OS 1:50,000 gazetteer or from the relevant index. Scales available are 1: 10,000 for moorland, 1:2500 for towns and semi rural areas and 1:1250 for cities. For further information see the user manual, or ask a member of staff.

1.7 Photocopies of National Grid Series sheets

Up to 4 copies of one A4 extract from any sheet can be supplied. If a larger portion is required written permission must be obtained from the OS, unless it is for a court case. If full-sized copies are required please see the brochure Reproductions Copy Services on top of the microfiche cabinets. When the maps are to be used for a court case a written statement should accompany the completed application form. For more details see the OS leaflet Copying of maps held in public libraries, or contact Ordnance Survey Copyright and Legal Affairs on 02380 792913.

2. The County Series (Mid 19th century to World War II)

The County Series covers the whole of the British Isles. For samples please see Harley, J.B. Ordnance Survey maps: a descriptive manual (1975). Maps Ref.G.2b.(13.)

2.1. The different scales

The 1:2500 scale (c.25’’ to one mile) plans were the largest scale plans published by the OS apart from town plans (OSTs: see below) and cover the whole of the British Isles except for mountain and moorland areas. The 1:10 560 (6’’ to one mile) scale is the largest to cover the whole of the British Isles and to show contours.

2.2. Finding the right sheet

2.2. (i) England and Wales

Consult the graphic indexes in the grey metal drawers to the left of the catalogue area of the Maps Reading Room, or older indexes at Maps Ref. Z.5a (1) and (2). The indexes show County Series sheetlines in red, with the National Grid lines underneath in grey. If a sheet is near a county boundary it could be bound in a volume of either county, so when ordering it is advisable to ask for sheets from both counties.

2.2 (ii) London

All the large scale London town plans are on the reference shelves in large bound volumes and microfilm. The indexes are in the grey metal drawers to the left in the catalogue area. The largest scale London plans (25 inches and 5 feet to a mile) have a rather complicated sheet numbering system that changes between editions. Click here for a guide to the correct indexes for each edition. 5 foot sheet numbers can also be derived from London County Council Names of streets and places (1955) at Maps Ref. (Desk), by looking up a street name.

2.2 (iii) Scotland

Use the index at Maps Ref.Z.5a.(9.), in the catalogue area of the Maps Reading Room. When ordering first editions the parish name must be quoted for some counties. (see list of editions at Reference Enquiry Desk). For the parish name see the indexes in the grey metal drawers in the catalogue area of the Maps Reading Room.

2.2. (iv) Ireland

Use the index at Maps Ref.Z.5a.(13.). When ordering First Editions for Dublin County the parish name must be quoted. For the parish name see the card index in the Reading Room on top of the microfiche cabinets.

2.3 Editions

2.3 (i) England, Wales and Scotland

The County Editions list refers specifically to the 1:2500 scale for England and Wales, but with a few exceptions the 1:10,560 editions were published around the same time as the 1:2500. The latest editions called Revised or ‘Further Revised’ usually have incomplete coverage as many of the sheets, especially for rural areas, were not published for financial reasons. If the sheet you want is not available at the 1:2500 scale, the area may be covered on the 1:10,560 series and vice versa. The London Editions list contains the most popular editions for london.

For England and Wales only, the OS editions file at the enquiry desk contains a more detailed listing of which sheets were covered by each revision.

2.3 (ii) Ireland

There is a list of editions of the 1:2500 scale maps in the Public Service Guide (blue binders behind the Reference Enquiry Desk) under Ireland. In addition, the CD-ROM catalogue contains entries for each individual county survey at this scale and at 1:10,560.

2.4 Ordering

2.4 (i) The 6" to 1 mile maps

There is no need to order the 6 inch (1:10,560) scale maps for England and Wales; not only are they all on microform but the volumes containing the original sheets are on open access on the low shelves around the sides of the Reading Room. They are shelved in alphabetical order by county name with sheet indexes at the front of each first edition volume. Sheets for Scotland and Ireland are stored in volumes in the basement and must be ordered.

2.4 (ii) The 25" to 1 mile maps

The County Editions list of 25" editions for England and Wales describes our holdings on microfiche (yellow = microfiche). The original 25 inch maps are all stored in the basement and have to be ordered up. The system will not allow you to order first edition 25 inch for England and Wales as these sheets are all available on fiche; if you need to see an original (for instance, to see the colours) you must fill in a paper application slip which must be signed by the Reading Room Curator.

The parish name must be quoted for some first editions.The County Editions list includes a "Parish" column which will tell you whether you need to order by parish name. There is a card index on top of the microfiche cabinets in the Reading Room which will tell you the parish name(s) corresponding to each sheet number for the appropriate counties. None of the sheets for Scotland or Ireland have been put on microfiche or microfilm.

2.5 Obtaining copies

Instant A4 printouts can be obtained from the reader-printers for any item which is on microfilm or fiche. Copies cost £1.50 each and a flexicard must be purchased from the Reference Enquiry Desk. If full sheets are required please see the brochure Reprographic Standard Services on top of the microfilm cabinets.

3. Ordnance Survey Town Plans (OSTs)

These were published for larger towns and cities at scales of 1:500, (c.10' to 1 mile), 1:528 (exactly 10' to 1 mile) and 1:1056 (5' to 1 mile) from about 1850 onwards. They were the largest scale plans for towns and cities published by the Ordnance Survey. Apart from important exceptions such as London, most were not published after 1900, but there was often more than one edition.

3.1 Finding the right sheet

3.1 (i) London

Sheet indexes for all editions of the 5' are in the drawer with the other London indexes.

3.1 (ii) Other town plans

For most towns all the sheets are contained in one volume. For major cities there are sheet indexes in the grey metal drawers in the catalogue area, just underneath the County Series indexes.

3.2 Editions

There is an inventory of all OSTs in the Public Service Guide Ordnance Survey section (blue binders) under the heading Town plans.

3.3 Ordering

All OSTs for towns throughout the British Isles are included in the Map Library's CD-ROM catalogue. This will give you the shelfmark ("Maps O.S.T." followed by a number) which you need to order the plan; it will also tell you if there is more than one edition.

3.4 Microform

The first edition London 1:2500 is on microfiche in the grey metal cabinets. All other editions of the 1:2500 and 5' (1:1056) London are on microfilm.

3.5 Obtaining copies

A4 extracts can be taken from the London microfiche and film. If full-sized copies are required please see the brochure Reproductions Copy Services on top of the microfiche cabinets.

4. Basic Reading List

Public Service Guide, Ordnance Survey Section (blue binders). Maps Ref.(behind Reference Enquiry Desk). Information on OS maps and history. See contents list next to Reference Enquiry Desk (black binder).

Harley, J. Brian, Ordnance Survey maps: a descriptive manual. (Southampton, 1975). Maps Ref.G.2.b.(13.). Contains a wealth of information with samples of sheets. Useful for symbols used on maps.

Harley, J.B. and Phillip, C.W. The Historian’s guide to Ordnance Survey maps (London, 1964). Maps Ref. G.2b.(8.). Excellent introduction to the subject. For further references see Reading List No.3 Ordnance Survey. Maps Ref.G.2b.(8.).

Oliver, Richard, Ordnance Survey maps: a concise guide for historians. London: Charles Close Society, 1993. Maps Ref. G.2b. (34.).