TOID
From Wikipedia, the free encyclopedia
A TOID (TOpographic IDentifier, pronounced toyed) is a 16–digit reference number assigned by the Ordnance Survey to identify a topographic feature in Great Britain.
Around 440 million man-made and natural features have been thus identified: buildings, roads, fields, phone boxes, pillar boxes, landmarks and many other types. The identification system is designed to be used in GIS, digital cartography and in any customized computer application, including non-cartographic ones, where fixed, real-world features need to be managed. Using consistent identifiers (IDs) makes it much easier to share data between various kinds of applications and systems. A TOID remains constant throughout the lifetime of the real-world feature it identifies, and is guaranteed not to be reassigned to anything else when the feature no longer exists.
Example: the TOID for the Tower of London is 0001000006032892.
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[edit] TOIDs in OS MasterMap
OS MasterMap, the Ordnance Survey's master database, depends on TOIDs. Every feature identified by a TOID in MasterMap is related to a polygon, defined in National Grid coordinates, which represents the area it occupies on the ground. Other attributes of the feature are defined by relating them, via GML, to the TOID. Users of MasterMap relate their own data to TOIDs of items of interest to them.
[edit] TOID revision history
If the data for a topographic feature is edited, for example to reflect a real-life change or to correct an error, then the changes are referenced by TOID. Unless the feature has undergone drastic change, the feature keeps its original TOID, enabling one to track changes to a topographic feature over time if one has access to the historic data.
[edit] Granularity of TOIDs
The granulaity of objects in the real world defined as TOIDs is not always what one might expect. Some things, such as "St Mary's football stadium, Southampton" or a typical detached house and its plot of land, correspond nicely to single TOIDs. However other more complex entities that seem to be well understood, such as Southampton Central railway station, are defined in terms of multiple TOIDs: one for the main building, several others for the platforms, and another for the pedestrian bridge over the tracks. There is no "supertoid" that unites them into one entity. This reflects an attitude to TOID definition more that of the surveyor than the tourist or commuter. But it also acknowledges that defining the boundaries of vaguely defined folk objects is subjective: should the station car-park be defined as part of the station, for example? The TOID scheme leaves such decisions to its users, that is, those building information systems for end-users.
[edit] Intellectual Property
Historically highly protective of its extensive intellectual property, aided through the special and somewhat arcane protection afforded to Crown copyright material, the Ordnance Survey has stated its policy on royalty free use of the TOID with the aim of allowing easier integration of data using its spatial database: a core part of its vision of a Digital National Framework.
"TOID" is a registered trademark of Ordnance Survey.
