Ordnance Survey (OS; often referred to as "the Ordnance Survey") is the national mapping agency for Great Britain and is one of the world's largest producers of maps. It is a non-ministerial government department, executive agency and trading fund of the Government of the United Kingdom, where it falls under the remit of the Department for Business, Innovation and Skills. It is also a member of the Public Data Group.The agency's name indicates its original military purpose (see ordnance and surveying): mapping Scotland in the wake of the Jacobite rebellion in 1745. There was also a more general and nationwide need in light of the potential threat of invasion during the Napoleonic Wars, reflected in the inclusion of the War Department's broad arrow in the agency's logo.Ordnance Survey mapping is usually classified as either "large-scale" (in other words, more detailed) or "small-scale". The Survey's large-scale mapping comprises maps at six inches to the mile or more (1:10,560, superseded by 1:10,000 in the 1950s) and was available as sheets until the 1980s, when it was digitised. Small-scale mapping comprises maps at fewer than six inches to the mile, such as the popular one inch to the mile "leisure" maps and their metric successors. These are still available in traditional sheet form.Ordnance Survey maps remain in copyright for fifty years after their publication. Some of the Copyright Libraries hold complete or near-complete collections of pre-digital OS mapping.