> For the complete documentation index, see [llms.txt](https://docs.os.uk/osngd/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/osngd/using-os-ngd-data/os-ngd-structures/field-boundary/field-boundary-attribution.md). # Field Boundary attribution {% hint style="info" %} The content on this page supplements that provided on the [Field Boundary Feature Type](/osngd/data-structure/structures/structure-features/field-boundary.md) page. {% endhint %} ## Height and width Vegetated field boundary features are given minimum, maximum and average (mean) height and width values. Values are rounded up to the nearest 0.5metres and provide an indication of the height or width rather than an absolute value. Consideration is given to the natural movement of these features and seasonal variances; therefore, during the calculation process, the Hedge width calculation includes a tolerance of 2.0metres, and the Tree Canopy and Wooded Strip width calculations include a tolerance of 3.0metres. The minimum, maximum and average height and width values are calculated using the 10th and 90th percentile values, sampled along the length of the Field Boundary feature at regular intervals. The calculated average mean value represents the most appropriate average height or width for each section of vegetated Field Boundary. Wall, Unknown and Other features are not given a height or width value. ## Imagery date The [Imagery Evidence Date attribute](/osngd/data-structure/structures/structure-features/field-boundary.md#imagery_evidencedate) is the date on which the latest imagery capture was gathered and used to identify the Field Boundary feature. Where a feature has not yet been classified, it is ‘Unknown’ and the Imagery Evidence Date will be 'null'. ## Woodland Boundary flag The [Is Woodland Boundary attribute](/osngd/data-structure/structures/structure-features/field-boundary.md#iswoodlandboundary) is a Boolean flag to identify whether a field boundary is adjacent to a land cover area classified as woodland. ‘Woodland’ is defined as a land cover polygon with a classification of Coniferous Trees and / or Non-Coniferous Trees. Vegetated Field Boundary features adjacent to an area of woodland in the OS NGD Land Theme, which include a classification of Coniferous Trees, Non-Coniferous Trees, Scattered Coniferous Trees or Scattered Non-Coniferous Trees, will have the Is Woodland Boundary attribute populated with ‘True’ and height and width values will be 'null'.
Example map showing Woodland areas with the 'Is Woodland Boundary' attribute highlighted in green for 'True' and in red for 'False'.

Example map showing Woodland areas with the 'Is Woodland Boundary' attribute highlighted in green for 'True' and in red for 'False'.

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