Please click on any of the definitions for a more detailed explanation. Unique Property Reference Number (UPRN)UPRN is an acronym for Unique Property Reference Number and is a unique twelve digit number assigned to every unit of land and property recorded by local government.BS7666BS7666 is a British Standard that sets out the guidelines upon which are built the Local Land and Property Gazetteers (LLPGs) and Local Street Gazetteers (LSGs).AddressBaseThe AddressBase range of Address datasets are an amalgamation of the NLPG, Ordnance Survey’s OS MasterMap® Address Layer 2 and the Royal Mail PAF by GeoPlace.Local Land and Property Gazetteer (LLPG)A Local Land and Property Gazetteer (LLPG) is a collection of address and location data created by a local authority. The data held by LLPGs is standardised to BS7666, which is then amalgamated with other LLPGs to form the National Land and Property Gazetteer (NLPG).GazetteerA gazetteer is a register of geographical information concerning places and locations, rivers, mountains and so on. This information is used in conjunction with maps, working as an index to the topographical and structure location information.Local Street Gazetteer (LSG)A Local Street Gazetteer (LSG) is a database of all street information. Each Local Street Gazetteer is compiled by one the 172 Highway Authorities in England and Wales. Information about the street will include many items such as its name, location, type and length.Associated Street Data (ASD)Associated Street Data (ASD) forms part of the National Street Gazetteer (NSG) and contains a wealth of addition information related to streets.National Land and Property Gazetteer (NLPG)The National Land and Property Gazetteer (NLPG) is a database containing within it over 32 million address records covering the whole of England and Wales. It is the amalgamation of all the BS7666 compliant address data held by local authorities that they have compiled within their Local Land and Property Gazetteers (LLPG).National Street Gazetteer (NSG)The National Street Gazetteer (NSG) is a database that holds information about all the streets in England and Wales. In addition to the name of the street it contains information such as its type, location and length. It is compiled from the Local Street Gazetteers (LSGs) that are created by each of the 172 Highway Authorities in England and Wales.Street Naming and Numbering (SNN)Street Naming and Numbering (SNN) is a statutory requirement for the department within a Council responsible for naming new streets and numbering new locations within that street.