Product attributes

Tile reference

The tile reference corresponds to the OS MasterMap Topography Layer 5 km tile to which the Building Height Attribute data applies. For consistency, the tile reference attribute will follow the 5 km naming convention adopted by OS MasterMap Topography Layer and Building Height Attribute data, for example:

• TQ2060 for TQ26SW

• TQ2065 for TQ26NW

• TQ2560 for TQ26SE

• TQ2565 for TQ26NE

TOID

Building Height Attribute data contains the unique feature references, or topographic identifiers (TOIDs), from the OS MasterMap Topography Layer. This enables associated Building and Structure Height data to be joined to the Topographic Area features within OS MasterMap Topography Layer.

The TOID is a persistent and unique identification string published in the OS MasterMap Topography Layer product. These identifiers have a prefix of ‘osgb’, are either 13 or 16 digits in length, and are allocated sequentially when a new building feature is created. TOIDS are retained throughout their lifecycle and are never re-assigned to a different feature. In order for these TOIDs to be consistent across all OS products, the identifier should not be altered in any way.

On occasion, a building TOID in OS MasterMap Topography Layer may have no corresponding height values in the Building Height Attribute data. This can occur due to the two products having different update cycles or in cases where a building has been constructed after the capture of the source Building Height Attribute data.

TOID version

The TOID version attribute represents the version of the OS MasterMap Topography Layer TOID for which the height values were calculated. The Building Height Attribute production process means that in certain cases the version number for a given TOID in the Building Height Attribute data may differ from the version number in the latest Topography holding. As the two products (OS MasterMap Topography Layer and OS MasterMap Topography Layer – Building Height Attribute) have different release schedules, this issue with version numbers can occur when a Topography Layer feature has been modified since the Building Height Attribute data values were calculated or because the most up-to-date version of OS MasterMap Topography Layer is not being used.

Building Height Attribute process date

The Building Height Attribute process date represents the date when the Building Height Attribute data was created.

Building Height Attribute data confidence level

Due to the derived nature of Building Height Attribute data using multiple capture methods and the current limitation of only being able to apply one height metric to a building or structure, we are aware there are circumstances where data accuracy may be impacted. Such circumstances include, but are not limited to, the following:

• Where a building or structure is situated on a hill

• Where a building or structure has multiple heights or is in direct proximity to another feature (for example, a tree or a river) that could impact the height reading

• Where a DSM is variable in the immediate area, such as in rural areas and mountains and moorland areas

Multiple quality checks are made on the data before release to mitigate any errors, and confidence levels are high on the dataset, but please verify or contact OS if any of the data does not look correct. We are confident that this is best dataset of its kind available in Great Britain, and the data is being constantly improved, but you may want to liaise with your appointed OS Technical Consultant if you want to use the data on a large-scale project where accuracy is key.