Features

1:250 000 Scale Colour Raster shows cities, towns, many villages, motorways, A and B roads, railways, rivers, and some woodlands across Great Britain.

Source and scale

1:250 000 Scale Colour Raster is derived from the 1:250 000 scale topographical digital database. It is designed to be nominally viewed at a 1:200 000 scale.

Coordinate reference system

1:250 000 Scale Colour Raster is available in British National Grid coordinates, which are expressed in metres relative to an origin set to a point west of the Isles of Scilly. These coordinates can easily be spatially related to other surveys, drawings, datasets, and Ordnance Survey products.

Coverage

Coverage of 1:250 000 Scale Colour Raster is all of Great Britain. It is supplied in 100km by 100km tiles aligned to the National Grid.

Where a line feature ends by intersecting the tile edge, it is matched with its corresponding feature on the adjacent tile so that both features end on the same unique coordinate. The representation of detail across the tile edge is of a cartographically acceptable standard when plotted or displayed at scale.

Product revision programme

1:250 000 Scale Colour Raster is updated via a continuous revision programme. The revision programme tracks real-world change, and is determined by assessing the following factors:

• Known surveyed change.

• Change intelligence gathered from a range of sources.

• How long it has been since an area was last revised.

Priority is given to prestige sites categorised as significant items of change, such as major road construction projects. Significant items of surveyed change relevant to the scale are captured during the revision programme.

Resolution

Each data tile is converted into a raster tile at a resolution of 10 dots per millimetre (dpmm)/254 dots per inch (dpi). One pixel represents 25 metres on the ground. This resolution maintains the necessary clarity of text.

Georeferencing is the process of registering the raster images within a geographic framework by assigning map coordinates to the image data and resampling the pixels of the image to conform to the map projection grid.

The 1:250 000 Scale Colour Raster supply is not georeferenced in any way. This means that when you load the tiles into a GIS, they will not be set up in geographic relationship to each other.

To view the map tiles in correct geographic relation to both the National Grid and the other tiles, you need to georeference the map tile files. Most geographic information systems (GIS) provide georeferencing functionality, but for each set of tiles you need to provide information on how the tiles should be ordered.

Ordnance Survey provides this information in a set of georeferencing files for 1:250 000 Scale Colour Raster. These files contain the National Grid corner coordinates for each 100km by 100km tile. You can download the files for free from the 1:250 000 Scale Colour Raster Downloads page. Please check which format your GIS supports before downloading. The TIFF World Files (TFW) are for use in ESRI® ArcGIS and the TAB files for use in MapInfo®. You should save the georeferencing files to the same directory as the map tile files to ensure that they work correctly. Great Britain is surveyed and mapped using the Transverse Mercator (or Gauss-Kruger) projection, so all raster tiles will be mapped to this projection (as it applies to the Ordnance Survey National Grid) when using the georeferencing files.

The 1:250 000 Scale Colour Raster product includes the 1:250 000 Scale Gazetteer containing approximately 25 500 points to help you find place names and locations. It covers the extent of the 56 100km by 100km tiles.

The information is provided as a single text file in ASCII text format and is included in the compressed download file.

The gazetteer area extent is as follows:

1:250 000 Scale Colour Raster product specification

Number of tiles in Great Bitain

56 (edge matched)

Tile size

100km by 100km

Coverage

Great Britain

Availability

National coverage (in a single download)

Resolution

254 dots per inch (dpi)

Data structure

Raster

Storage volumes (GB coverage)

128 MB (compressed)

130 MB (uncompressed)

Update frequency

Quarterly: Annually (June)

Product legend

Gazetteer

The 1:250 000 Scale Gazetteer includes approximately 25 500 points that cover the extent of the 56 100km by 100km tiles. The information is provided as a single file in ASCII text format and is included in the compressed download file.

Additional technical information

Additional information, common to all colour raster map products is available through the Colour Raster Map Core principle pages. These pages provide an overview of the product and a technical specification covering:

The 1:250 000 Scale Colour Raster product is a small-scale, digital, raster mapping product that gives a regional view similar in content and appearance to a typical road atlas. It clearly shows the landscape features relevant to its scale, including cities, towns, many villages, motorways, A and B roads, railways, rivers, and some woodlands across Great Britain. You can use 1:250 000 Scale Colour Raster to overlay your own geographic or business data, or use it as a standalone map.

Product highlights

The 1:250 000 Scale Colour Raster product:

• Is an ideal regional overview or backdrop map.

• Has classic road atlas styling:

  • Motorways and main roads stand out, but you can also see country lanes clearly.

  • Places of interest, including camping and caravan sites, are clearly shown.

  • Road and junction numbers, junction-to-junction mileage, and primary routing are included.

• Is compatible with other open datasets available from data.gov.uk and many other sources.

Product applications

1:250 000 Scale Colour Raster combines cities, towns, motorways, A and B class roads, railways, rivers, and other key features. This makes it the ideal geographic context on which to overlay your own business data or to use in your applications.

1:250 000 Scale Colour Raster can be used for:

• Route planning

• Geographic context

• Webpage enhancement

A digital legend (key) that explains the cartographic symbols and styles is supplied with the product:

• English version of the 1:250 000 Scale Colour Raster legend

• Welsh version of the 1:250 000 Scale Colour Raster legend

Package inclusions

The compressed download file includes (among others):

• 56 edged-matched individual 100km by 100km tiles aligned to the National Grid.

• Product legend in TIFF and PDF format.

• 1:250 000 scale gazetteer

Ordnance Survey National Grid

Ordnance Survey divides Great Britain into squares of 100km by 100km. Each square has a unique two-letter reference, for example, TG in the grid below. 1:250 000 Scale Colour Raster tiles are identified by the National Grid reference of the south-west corner of the 100km² area they cover.

An introductory guide to the British National Grid (BNG) is available on the OS website.

1:250 000 Scale Colour Raster is a small-scale, digital, raster mapping product giving a regional view, similar in content and appearance to a typical road atlas. It clearly shows the landscape features relevant to its scale, including cities, towns, many villages, motorways, A and B roads, railways, rivers, and some woodlands across Great Britain. You can use 1:250 000 Scale Colour Raster to overlay your own geographic or business data, or use it as a standalone map.

How to get this product

Visualise 1:250 000 Scale Colour Raster data online

1: 250 000 Scale Colour Raster - Welsh map symbols legend

1: 250 000 Scale Colour Raster - Map symbols legend

The legend for 1: 250 000 Scale Colour Raster is available as a PDF below.

1: 250 000 Scale Colour Raster - Welsh map symbols legend

The Welsh language legend for the 1:250 000 Scale Colour Raster is available as a PDF below.

1: 250 000 Scale Colour Raster - Map symbols legend

1:250 000 Scale Colour Raster – Georeferencing TFW files

Georeferencing files put tiles of map data in their correct position when opened in a GIS. TIFF World Files (TFW) can be used to georeference raster data in ESRI® ArcGIS. 100km x 100km.

1:250 000 Scale Colour Raster – Georeferencing TAB files

Georeferencing files put tiles of map data in their correct position when opened in a GIS. TAB files are for use with MapInfo. 100km x 100km.