1:25 000 Scale Colour Raster Technical Specification

This technical specification provides detailed technical information about 1:25 000 Scale Colour Raster. It is targeted at technical users and software developers.

The following pages contain information about 1:25 000 Scale Colour Raster, including file compression, legends, georeferencing and formats.

1:25 000 Scale Colour Raster Specification

Number of tiles in Great Britain

2,859 (edge matched)

• England: 1,508

• Scotland: 1,130

• Wales: 289

Tile size

10 km by 10 km

Availability

National coverage

Resolution

254 and 660 dots per inch

Data structure

Raster

Transfer formats

• TIFF PackBits compressed

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

• GeoTIFF with LZW* compression

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

Storage volumes per tile

0.2–9 Mb compressed

Update frequency

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

Product legend

Maintained versions (in English and Welsh) of the 1:25 000 Scale Colour Raster legend, which defines all of the map symbols used in the product, can be found on the 1:25 000 Scale Colour Raster Product Support page of the OS website:

• English version of the 1:25 000 Scale Colour Raster legend

• Welsh version of the 1:25 000 Scale Colour Raster legend

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 on the OS website.

Index

• Georeferencing information

• Image file directory entries

• Product glossary