The British Ordnance Survey, now a civilian agency, retains its name from its origin as a military topographic survey of Britain during the Napoleonic Wars.
Do not confuse with ordinance.
A reduced form of ordinance, which is attested from the late 14th century in the sense of "military equipment or provisions". The sense of "artillery" arises in the early 15th century, the sense "military logistics" in the late 15th century. The shortened form ordnance arises by the 17th century, now distinct in meaning from the surviving meanings of ordinance.