GB Overview Maps Technical Specification

This technical specification provides detailed technical information about GB Overview Maps Scale Colour Raster. It is targeted at technical users and software developers.

Ordnance Survey's GB Overview Maps are a pair of small-scale maps designed predominantly for screen use. They provide geographic context for the whole of Great Britain by showing the major boundaries, a spread of towns and cities, hill shading, road networks and national parks.

GB Overview Maps are derived from our MiniScale data and supplied in raster format (GeoTIFF). The raster files can also be used for web applications or within a geographical information system (GIS) as a backdrop.

GB Overview Maps are most suited for viewing on screen, but can also be used for simple publications.

Product Specification.

Files

2 single TIFF image files, one for each map.

Coverage

Great Britain

Availability

National coverage (in a single download)

Scale

1: 5 000 000

Resolution

254 dots per inch (dpi)

Data structure

Raster

Storage volumes (Great Britain coverage)

• 2,148 KB (compressed) GB Overview

• 2,902 KB (compressed) GB OverviewPlus

Update frequency

Annually (January)

Coordinate reference system

British National Grid (OSGB36)

Additional technical information

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

• Georeferencing

• Image file directory (TIFF)

• Product glossary