Unique identifiers

The OS NGD primarily uses a new identifier called the OSID (OS Identifier) to uniquely identify features. The OSID is used persistently and allows the unique identification of records in the OS NGD. It should be noted that the OSID is not unique across the OS NGD, but rather is only unique at a feature type level. The reason for this is, when possible, the same OSID will be used on multiple features when they represent the same geographical feature. For example, a point feature in the OS NGD Geographical Names Theme which represents a water body will have the same OSID as the more detailed water body representation in the OS NGD Water Features Theme.

Other unique identifiers are also present in the OS NGD. These include the UPRN (Unique Property Reference Number) and USRN (Unique Street Reference Number). These remain the unique identifiers in our data to represent Address and Local Authority Street records, respectively.

The TOID (Topographic Identifier) is also present in the OS NGD, but in most instances this is an optional attribute and therefore should not be relied upon to complete data linking or for implementing COUs. The reason for this identifier being optional is the improved currency on which the OS NGD will be published, meaning the TOID which is created in our existing OS product systems will not always be allocated to features as frequently as they will be accessible via the OS NGD.