Ordnance Survey measures the data in its products in one or more of the ways set out in the definitions of data measures table below.
| Data measure | Definition | Sub-measure | Definition |
|---|---|---|---|
* When testing the data according to the dataset specification against the ‘real world’ or reference dataset.
Metadata, which is ISO 19115 UK GEMINI 2 compliant, can be found at https://www.data.gov.uk/dataset/e3d9cd8e-e702-4fc6-a674-c1f25eb5efab/ordnance-survey-code-point-open. Metadata .xml files can be found at http://www.ordnancesurvey.co.uk/oswebsite/xml/products/.
Completeness
Presence and absence of features against the specified data content
Omission
Features representing objects that conform to the specified data content but are not present in the data.
Commission
Features representing objects that do not conform to the specified data content but are present in the data.
Logical consistency
Degree of adherence to logical rules of data structure, attribution and relationships
Conceptual consistency
How closely the data follows the conceptual rules (or model).
Domain consistency
How closely the data values in the dataset match the range of values in the dataset specification.
Format consistency
The physical structure (syntax): how closely the data stored and delivered fits the database schema and agreed supply formats.
Topological consistency
The explicit topological references between features (connectivity) – according to specification.
Positional accuracy
Accuracy of the position of features
Absolute accuracy
How closely the coordinates of a point in the dataset agree with the coordinates of the same point on the ground (in the British National Grid reference system).
Relative accuracy
Positional consistency of a data point or feature in relation to other local data points or features within the same or another reference dataset.
Geometric fidelity
The ‘trueness’ of features to the shapes and alignments of the objects they represent*.
Temporal accuracy
Accuracy of temporal attributes and temporal relationships of features
Temporal consistency
How well-ordered events are recorded in the dataset (lifecycles).
Temporal validity (currency)
Validity of data with respect to time: the amount of real-world change that has been incorporated in the dataset that is scheduled for capture under current specifications.
Thematic accuracy
Classification of features and their attributes
Classification correctness
How accurately the attributes within the dataset record the information about objects*.