science

TOID

TOID is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand TOID rather than just read about it. In short: A TOID (for "TOpographic IDentifier", pronounced toyed) is a unique identifier assigned by the Ordnance Survey to identify every topographical feature in Great Britain. Topographical identifier A TOID consists of two parts: a prefix ‘osgb’, and a unique identifier that is 13-16 digits long.

Key takeaways

TOID belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect TOID to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TOID from memory before moving on to harder problems.

Reference excerpt

A TOID (for "TOpographic IDentifier", pronounced toyed) is a unique identifier assigned by the Ordnance Survey to identify every topographical feature in Great Britain.

Topographical identifier A TOID consists of two parts: a prefix ‘osgb’, and a unique identifier that is 13-16 digits long. For example, the TOID for the Tower of London is osgb1000006032892. In GML 2, a TOID is encoded as a gml:fid (Feature Identifier); in GML 3 as a gml:id. 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 information about fixed, real-world features needs 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. In OS MasterMap, Ordnance Survey's master database, every feature is identified by a TOID. Other attributes of the feature are defined by relating them, via GML, to the TOID. Users of OS MasterMap relate their own data to TOIDs of the relevant items. This allows organisations to share data easily and cheaply since TOIDs are maintained centrally by Ordnance Survey, and are free to reuse.

Granularity of TOIDs Every object in OS MasterMap has its own TOID, including features representing buildings, roads, addresses, and cartographic text. Complex entities 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. The OS MasterMap Sites Layer has a single TOID for these 'sites'. Similarly, users can create their own "superTOID" that unites features into one entity. This 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.

TOID revision history If the data for a 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 feature over time if one has access to the historic data.

Intellectual property In keeping with other OS open data initiatives, Ordnance Survey has a 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.

See also Unique Property Reference Number (UPRN) Unique Street Reference Number (USRN)

References

External links

OS MasterMap SpatialNews Press Release: Ordnance Survey - The new heart of Britain's mapping Archived 3 March 2016 at the Wayback Machine

Worked examples

Example 1 — a first encounter with TOID

Start with the simplest possible case. Write down what TOID claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to TOID before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about TOID ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of TOID

In research: TOID appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses TOID in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: TOID is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geographic object identifiers, Identifiers, Ordnance Survey, so understanding it makes those chapters shorter.
In everyday life: Look for TOID outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study TOID in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TOID means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain TOID out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TOID in simple terms?

A TOID (for "TOpographic IDentifier", pronounced toyed) is a unique identifier assigned by the Ordnance Survey to identify every topographical feature in Great Britain. Topographical identifier A TOID consists of two parts: a prefix ‘osgb’, and a unique identifier that is 13-16 digits long.

Why does TOID matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study TOID?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on TOID.