# 1:50 000 Scale Colour Raster Technical Specification

## 1:50 000 Scale Colour Raster product specification

### Number of tiles in Great Britain

820 (582 sea tiles)

### Tile size

20km by 20km

### Availability

National coverage

### Resolution

254 and 660 dots per inch

### Data structure

Raster

### Transfer format

* TIFF-PackBits
* TIFF-LZW 
* GeoTIFF
* Windows**®** BMP

### Storage volumes per tile

0.3–18 Mb

### Update frequency

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

## Product legend <a href="#id-2.-product-legend" id="id-2.-product-legend"></a>

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](/os-downloads/products/maps-and-imagery-portfolio/1-50-000-scale-colour-raster/1-50-000-scale-colour-raster-downloads.md).

## Common mapping abbreviations used in the product <a href="#id-2.1-common-mapping-abbreviations-used-in" id="id-2.1-common-mapping-abbreviations-used-in"></a>

A full list of the common mapping abbreviations used in 1:50 000 Scale Colour Raster is available from the [Abbreviations used on OS 1:25 000 and 1:50 000 scale mapping page](/os-downloads/products/maps-and-imagery-portfolio/maps-and-imagery-fundamentals/maps-and-imagery-products-technical-specification/abbreviations-used-on-os-1-25-000-and-1-50-000-scale-mapping.md).

## Additional technical information

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

* [Georeferencing](/os-downloads/products/maps-and-imagery-portfolio/maps-and-imagery-fundamentals/maps-and-imagery-products-technical-specification/georeferencing.md)
* [Image file directory (TIFF)](/os-downloads/products/maps-and-imagery-portfolio/maps-and-imagery-fundamentals/maps-and-imagery-products-technical-specification/image-file-directory-tiff.md)
* [Abbreviations used on OS 1:25 000 and 1:50 000 scale mapping](/os-downloads/products/maps-and-imagery-portfolio/maps-and-imagery-fundamentals/maps-and-imagery-products-technical-specification/abbreviations-used-on-os-1-25-000-and-1-50-000-scale-mapping.md)
* [Product glossary](/os-downloads/products/maps-and-imagery-portfolio/maps-and-imagery-fundamentals/maps-and-imagery-products-technical-specification/product-glossary.md)


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