Street_USRN_TopographicArea_TOID_4

This page aims to provide all the information to evaluate if the method of associating the respective identifiers is suitable for your needs. These identifier relationships have been extracted from existing premium products and are presented in a standalone table for easy and open access to the information. It describes which product the information was extracted from, what information was extracted and how the source product derived the original association between the identifiers.

Identifiers displayed on OS Map data showing RoadLink and Topographic area feature types

Relationship Extraction

This relationship is between the Unique Street Reference Number (USRN) of the Street features in OS MasterMap Highways Network and the TOID of the TopographicArea of the corresponding road surface area in OS MasterMap Topography Layer.

A USRN is a unique, persistent identifier for every street, assigned in the National Street Gazetteer (NSG) to any road, footway, path, cycle track, track or passageway that forms a highway. Where possible, the geometry of streets provided in the National Street Gazetteer is spatially matched to the geometry of OS RoadLinks to provide the additional attribution captured in the NSG against detailed OS geometry.

This relationship is extracted from the relatedRoadArea attribute on the matched RoadLink(s) within OS MasterMap Highways Network – Roads product following its release. This means that this relationship will not include all USRNs in OS MasterMap Highways Network, as Street features that have not been matched to an OS RoadLink will be omitted.

Correlation Method

Where Street features have been successfully matched to OS RoadLinks, the Street features in OS MasterMap Highways Network are aggregate features composed of one or more RoadLinks. The relationship is determined by a line in a polygon intersection between the centre line geometry of matched RoadLink(s) and the topographic area polygon. The relationship is performed by Ordnance Survey.

The two source products used to extract this relationship are on different refresh cycles. OS MasterMap Highways Network is updated monthly, whereas OS MasterMap Topography Layer is updated every six weeks. Therefore, some of the version information in the product may have changed, meaning that the relationship is out of sync. A Confidence Value is assigned to indicate the reliability of the version information provided in this product in relation to the version of the features used to form the correlation in the original product. The Confidence Value is given for each relationship, which is defined in this relationship as:

Confidence Value	Definition
Version information is correct	The version information provided is the same as the version of the feature used to create the correlation.
Version information has potentially changed	The version information could be different from the version of the feature that was used to create the correlation.
Version information has changed	The version information provided is different from the version of the feature used to create the correlation.