1:50 000 Scale Colour Raster Technical Specification

This technical specification provides detailed technical information about the 1:50 000 Scale Colour Raster. It is targeted at technical users and software developers.

1:25 000 Scale Colour Raster product specification

Number of tiles in Great Britain

816 (edge matched)

• England: 421

• Scotland: 338

• Wales: 86

Tile size

20km by 20km

Availability

National coverage

Resolution

254 and 660 dots per inch

Data structure

Raster

Transfer format

• TIFF palette 8-bit (256 colours) LZW* uncompressed

• TIFF palette 8-bit (256 colours) with LZW* compression

• GeoTIFF with LZW* compression

• Windows® BMP 8-bit colour (256 colours) uncompressed

* If LZW compressed formats are used, then registration may be required. Information is available on the Unisys® website.

Storage volumes per tile

0.3–18 Mb

Update frequency

Quarterly: March, June, September and December (change-only updates)

Product legend

Maintained versions (in English and Welsh) of the 1:50 000 Scale Colour Raster legend, which defines all of the map symbols used in the product, can be found on the 1:50 000 Scale Colour Raster Downloads page.

Common mapping abbreviations used in the product

A full list of the common mapping abbreviations used in 1:25 000 Scale Colour Raster is available in the shared Colour Raster Map Technical Specification.

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:

• Georeferencing
• Image file directory (TIFF)
• Product glossary