# Data measures
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 |
| ----------------------- | ------------------------------------------------------------------------------------- | -------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **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\*. |
\* When testing the data according to the dataset specification against the ‘real world’ or reference dataset.
## Metadata
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.](http://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/.](http://www.ordnancesurvey.co.uk/oswebsite/xml/products/)
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