> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/products/buildings-and-infrastructure-portfolio/os-open-linked-identifiers/os-open-linked-identifiers-overview/product-details.md).

# Product details

## Feature types <a href="#bookmark15" id="bookmark15"></a>

<table><thead><tr><th width="194">Feature Type</th><th>Identifier Type</th><th>Source Product</th><th>Description</th></tr></thead><tbody><tr><td>TopographicArea</td><td>TOID</td><td>OS MasterMap Topographic Layer</td><td>Polygon limited to either a building outline or road surface area.</td></tr><tr><td>RoadLink</td><td>TOID</td><td>OS MasterMap Highways</td><td>Section of road from junction to junction.</td></tr><tr><td>Road</td><td>TOID</td><td>OS MasterMap Highways</td><td>Collection of RoadLink with a given name.</td></tr><tr><td><p>BLPU</p><p>(Building Land Parcel Unit)</p></td><td><p>UPRN</p><p>(Unique Property Reference Number)</p></td><td>AddressBase Premium</td><td>An address location with postal address.</td></tr><tr><td>Street</td><td><p>USRN</p><p>(Unique Street Reference Number)</p></td><td>OS MasterMap Highways</td><td>An identifier allocated to a street by a local authority.</td></tr><tr><td>ORRoadLink/ ORRoadNode</td><td>GUID</td><td>Open Roads</td><td>Road sections and junctions from our open data product. These features are referred to in OS Open Roads as RoadLink and RoadNode. In this product they are referred to as ORRoadLink and ORRoadNode respectively to distinguish them from the OS MasterMap Highways Networks RoadLink and RoadNode features.</td></tr></tbody></table>

Please refer to the source product documentation for details of each feature that is being related.

## Identifier Schemes <a href="#bookmark16" id="bookmark16"></a>

Each feature uses a specific identifier scheme for its identifier. These are as follows:

* Unique Property Reference Number (UPRN)

A UPRN is a unique numeric identifier for every address in Great Britain. The identifier is critical and can be found throughout OS's AddressBase products. It provides a complete and consistent

identifier throughout a property’s life cycle. This means the UPRN is assigned to an address at the earliest opportunity and is never reused, even after the property has been demolished.

* Unique Street Reference Number (USRN)

A USRN is a unique and persistent identifier for every street, road, track, path, cycletrack or way in Great Britain and can be found in OS’s Highways Network products and is also a key component in OS’s AddressBase suite of products.

* Topographic Identifier (TOID)

A TOID is a unique identifier, consisting of the letters ‘osgb’ and followed by either thirteen or sixteen digits, associated with every feature in many of Ordnance Survey’s large-scale products. No amends can be made to this code as it may no longer be functional with other OS MasterMap products.

The TOID is based on the Digital National Framework concept and the principles that underpinned it.

These identifiers contain no attribution or information, for example coordinate position. If you need this to visualise your data, we offer a family of Open Identifier products for you to download and freely use under Open Government Licence.

## Relationship Source <a href="#bookmark17" id="bookmark17"></a>

The following table lists each of the relationships provided and the premium product the relationship has been extracted from.

| Correlation Method ID                    | Source Product for relationship        |
| ---------------------------------------- | -------------------------------------- |
| RoadLink\_TOID\_TopographicArea\_TOID\_2 | OS MasterMap Highways Networks - Roads |
| Road\_TOID\_TopographicArea\_TOID\_3     | OS MasterMap Highways Networks - Roads |
| Street\_USRN\_TopographicArea\_TOID\_4   | OS MasterMap Highways Networks - Roads |
| BLPU\_UPRN\_TopographicArea\_TOID\_5     | AddressBase Premium                    |
| RoadLink\_TOID\_Road\_TOID\_7            | OS MasterMap Highways Networks - Roads |
| RoadLink\_TOID\_Street\_USRN\_8          | OS MasterMap Highways Networks - Roads |
| BLPU\_UPRN\_RoadLink\_TOID\_9            | AddressBase Premium                    |
| Road\_TOID\_Street\_USRN\_10             | OS MasterMap Highways Networks - Roads |
| BLPU\_UPRN\_Street\_USRN\_11             | AddressBase Premium                    |
| ORRoadLink\_GUID\_RoadLink\_TOID\_12     | OS MasterMap Highways Networks - Roads |
| ORRoadNode\_GUID\_RoadLink\_TOID\_13     | OS MasterMap Highways Networks - Roads |

Please refer to the OS Open Linked Identifiers Technical Specification for details on how these relationships were extracted and how the original relationships were formed.

## General Structure <a href="#bookmark18" id="bookmark18"></a>

The Open Linked Identifier data product is supplied in Comma-Separated Value (CSV) format, which comes with Product Version Information files formatted as JavaScript Object Notation (JSON).

Upon downloading the data, you will receive zip files of the eleven Linked Identifier relationships. The generalised naming convention for each Relationship ID is:

*{Data Identifier 1}\_{Feature Identifier 1}\_{Data Identifier 2}\_{Feature Identifier 2}\_{CorrelationType Number}*

For example: *BLPU\_UPRN\_RoadLink\_TOID\_9*

| Relationship IDs                         | Relationship                                   |
| ---------------------------------------- | ---------------------------------------------- |
| RoadLink\_TOID\_TopographicArea\_TOID\_2 | RoadLink <-> TopographicArea                   |
| Road\_TOID\_TopographicArea\_TOID\_3     | Road <-> TopographicArea                       |
| Street\_USRN\_TopographicArea\_TOID\_4   | Street <-> TopographicArea                     |
| BLPU\_UPRN\_TopographicArea\_TOID\_5     | BLPU <-> TopographicArea                       |
| RoadLink\_TOID\_Road\_TOID\_7            | RoadLink <-> Road                              |
| RoadLink\_TOID\_Street\_USRN\_8          | RoadLink <-> Street                            |
| BLPU\_UPRN\_RoadLink\_TOID\_9            | BLPU <-> RoadLink                              |
| Road\_TOID\_Street\_USRN\_10             | Road <-> Street                                |
| BLPU\_UPRN\_Street\_USRN\_11             | BLPU <-> Street                                |
| ORRoadLink\_GUID\_RoadLink\_TOID\_12     | Open Roads RoadLink <-> OSMM Highways RoadLink |
| ORRoadNode\_GUID\_RoadLink\_TOID\_13     | Open Roads RoadNode <-> OSMM Highways RoadLink |

#### Comma-Separated Values <a href="#bookmark19" id="bookmark19"></a>

Upon downloading the CSV data, you will have 11 zip packages for each relationship. Each zip package contains 4 files, for example BLPU\_UPRN\_RoadLink\_TOID\_9.zip extracts:

<figure><img src="/files/tVV0T4bp0ep8zhPR0sgZ" alt="Extracted zip package showing four available files in .csv, .pdf, .json, and .txt formats"><figcaption><p>Four files extracted from BLPU_UPRN_RoadLink_TOID_9.zip</p></figcaption></figure>

| File                                             | Description                  |
| ------------------------------------------------ | ---------------------------- |
| BLPU\_UPRN\_RoadLink\_TOID\_9.csv                | Linked Identifier data (CSV) |
| BLPU\_UPRN\_RoadLink\_TOID\_9\_versions.json     | Product version information  |
| Licence.txt                                      | OGL Licence                  |
| UPRN\_RoadLink\_TOID\_9\_202001\_description.pdf | Product description          |

## Supply and Update <a href="#bookmark22" id="bookmark22"></a>

OS Open Linked Identifiers will be updated through a full supply on a six-weekly basis in line with AddressBase Premium. Each OS Open Linked Identifiers release will follow shortly after the corresponding AddressBase Premium release.

## Coverage and File Sizes <a href="#bookmark23" id="bookmark23"></a>

The product is released with full Great Britain coverage. As the product has been separated into individual zip files per relationship, each zip file size is dependent on the relationship it holds. The sizes range from a few hundred megabytes to 5-8 giga bytes. Please see the product listing on the OS Data Hub for accurate individual file sizes.


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