Ordnance Survey (OS) is a national mapping agency in the United Kingdom which covers the island of Great Britain. It is one of the world's largest producers of maps. Since 1 April 2015 it has operated as Ordnance Survey Ltd, a government-owned company, 100% in public ownership. The Ordnance Survey Board remains accountable to the Secretary of State for Business, Energy and Industrial Strategy.

• https://en.wikipedia.org/wiki/Ordnance_Survey
• https://www.ordnancesurvey.co.uk/