Ordnance Survey – Great Britain's national mapping agency
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These pages contain essential information and tools for not only professional users of geographic information in Great Britain, but any user of GPS and Ordnance Survey mapping.
Our online guide to coordinate systems in Great Britain introduces a number of important concepts including coordinate formats and transformations, and also acts as the user manual for our projection and transformation spreadsheet.
There is also a guide to the National Grid and some common FAQs.