The OS MasterMap is the premier digital product of the

Ordnance Survey The Ordnance Survey (OS) is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see Artillery, ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of ...

. It was launched in November 2001. It is a

database In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...

that records every fixed feature of

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

larger than a few meters in one continuous digital map. Every feature is given a unique TOID (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 measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...

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 Ordnance Survey claims that OS MasterMap data is never more than six months out of date, thanks to continuous review.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, pedestrian streets, parks, reserves to museums. It contains attributes to enable the routing of vehicles, taking into account the limitations of the road network in general.

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 Layer is a part of the National Spatial Address Infrastructure and contains National Land and Property Gazetteer attributes that classify properties. It is currently at the center 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 25 cm resolution aerial photos.

Delivery of the geographical data

OS MasterMap's data is in GML format. It is usually delivered as files compressed with gzip (providing 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 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 or digital data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data. It is a core function and fundamental component of computers. The cent ...

and

digital preservation In library science, library and archival science, digital preservation is a formal process to ensure that digital information of continuing value remains accessible and usable in the long term. It involves planning, resource allocation, and appli ...

, 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 website, 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 of MasterMap supply

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