About sample data

Downloading the data

Clicking on a link to a downloadable file generates a prompt by your browser asking you whether you wish either to open the file or to save it to your computer. We recommend that you save it to a suitable location on your computer.

Once the download is complete, browse to the downloaded file and double-click (or command-click) to open the archive file; you will be prompted to unzip and save its contents: Unless you specify another location, the unzipped files will be saved to your temp folder.

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Using the data

Ordnance Survey digital map data is supplied in vector and raster spatial data models and in a variety of file formats.

Vector data represents objects as coordinates at the ends of line segments, points, text position and so on. A series of line segments that returns to the same starting point form an area or polygon. The vector data model is more sophisticated than raster data because elements can be uniquely identified and the relationships between them are stored in a database.

Raster data is based on the division of reality into a regular grid of cells or pixels, with spatial position implicit in the ordering of the pixels. There is a number of formats used for the standard supply of raster data, of which TIFF and BMP are the most well known. Others are GIF, PCX and CCITT.

The two formats used for the standard supply of Ordnance Survey vector data are NTF and DXF^™. NTF is a British Standard (BS 7567) for the transfer of geographical data that is administered by the British Standards Insititution. DXF is a format for transferring drawings between CAD systems that is widely used as a de facto standard in the engineering and construction industries.

DXF is a trademark of Autodesk Incorporated.

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