The OS MasterMap is the premier digital product of the
Ordnance Survey
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. It was launched in November 2001. It is a
database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...
that records every fixed feature of
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
larger than a few meters in one continuous digital
map
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...
. Every feature is given a unique
TOID A TOID ( TOpographic IDentifier, pronounced ''toyed'') is a unique reference identifier assigned by the Ordnance Survey to identify every topographical feature in Great Britain.
Topographical identifier
A TOID consists of two parts: a prefix ‘os ...
(TOpographical IDentifier), a simple identifier that includes no semantic information. Typically each TOID is associated with a polygon that represents the area on the ground that the feature covers, in
National Grid coordinates. OS MasterMap is offered in themed "layers", for example a road layer and a building layer, each linked to a number of TOIDs. Pricing of licenses for OS MasterMap data depends on: the total
area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape
A shape or figure is a graphics, graphical representation of an obje ...
requested, the layers licensed, the number of TOIDs in the layers, the period in years of the data usage.
OS MasterMap can be used to generate maps for a vast array of purposes. Although the scale on a digital map is much more flexible than a paper map, one can print out maps from OS MasterMap data with detail equivalent to a traditional 1:1250 paper map.
Ordnance Survey claims that OS MasterMap data is never more than six months out of date, thanks to continuous review. The scale and detail of this mapping project is so far unique. Around 440 million TOIDs have so far been assigned, and the database stands at 600 terabytes in size.
Layers
Topography Layer
The OS MasterMap Topography Layer represents topography at a scale of 1:1250. It is further subdivided into a number of themes: land area classifications' buildings, roads, tracks and paths, rail, water, terrain and height, heritage and antiquities, structures; and administrative boundaries.
Integrated Transport Network Layer
OS MasterMap® Integrated Transport Network™ (ITN) Layer maps Great Britain’s road network – from motorways to pedestrian streets. It contains attributes to enable the routing of vehicles, taking into account the limitations of the road network.
OS MasterMap Address Layer 2
OS MasterMap Address Layer 2 is a dataset that describes the location of addresses. It is designed to be used as a means of geo-referencing addresses and attempts to improve on
Address Point Address Point is a mapping/GIS data product supplied by Great Britain's national mapping agency, Ordnance Survey. It is based on the UK’s postal mail organisation, the Royal Mail, list of postal addresses, Postcode Address File (PAF). The most sig ...
. Address Layer is a part of the
National Spatial Address Infrastructure The National Spatial Address Infrastructure (NSAI) was a database proposed by the UK Office of the Deputy Prime Minister (ODPM) on 26 May 2005 with the intention of creating a single repository of addresses for the UK. The proposal encountered nume ...
and contains
National Land and Property Gazetteer
The National Land and Property Gazetteer (NLPG) is an initiative in England and Wales to provide a definitive and consistent address infrastructure. Up until recently Great Britain has not held a single list of all addresses in the country, meaning ...
attributes that classify properties. It is currently at the centre of a dispute between Ordnance Survey and Intelligent Addressing, the custodian of the National Land and Property Gazetteer dataset.
Imagery Layer
The Imagery layer is a national collection of 25cm resolution aerial photos.
OS MasterMap Imagery Layer
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Delivery of the data
OS MasterMap data is in GML format. It is usually delivered as files compressed with gzip
gzip is a file format and a software application used for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and in ...
(giving them an extension 'gz').
Recently, Ordnance Survey has been trialing delivery of OS MasterMap data using WFS and WMS, in accordance with the Open Geospatial Consortium. This trial may even end up with automatic updates using WFS-T.
Custodianship of the data
Although branded like a commercial product, OS MasterMap is in fact the UK’s most complete, accurate and up-to-date geographic record. By moving to purely digital media for mapping, Ordnance Survey brings upon itself the responsibility of being the sole ''mandatory'' custodian of Great Britain's official maps. Previously, by virtue of being a publication on paper, a copy of every edition of every paper map published by Ordnance Survey would have been deposited, by law, with each of the six legal deposit
Legal deposit is a legal requirement that a person or group submit copies of their publications to a repository, usually a library. The number of copies required varies from country to country. Typically, the national library is the primary reposit ...
libraries in the UK. Although there is no such law in place for digital maps, the Ordnance Survey makes annual 'snapshots' of the data and voluntarily deposits with the legal deposit libraries:
The data, like any other, is susceptible to all the problems of computer data storage
Computer data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data (computing), data. It is a core function and fundamental component of computers.
The central pro ...
and digital preservation
In library and archival science, digital preservation is a formal endeavor to ensure that digital information of continuing value remains accessible and usable. It involves planning, resource allocation, and application of preservation methods an ...
, for example: data corruption; the question of how often to take snapshots of the data (i.e. should every edit be recorded?); access to old versions of the data; practicable access to old versions of the data (after format changes, will new software be able to read old data?).
References
External links
* {{Official, https://www.ordnancesurvey.co.uk/business-and-government/products/mastermap-products.html
The Guardian: Devil is in the detail as OS maps out the future by Paul Brown, March 8, 2004
Example GIS application of Web Based Asset Management and MasterMap supply
Geographical databases in the United Kingdom
Maps from Ordnance Survey
Maps of the United Kingdom
2001 works