OS NGD Land Cover enhancements

A Lightning Talk

What layers form Land Cover enhancements?

Land

Structures

Road, Tracks or Paths

Rail

Water

click the above images to enlarge them

What formats does the Land Cover enhancements data come in?

The Land Cover enhancements in OS NGD come in the form of cross reference files for the five feature types that are part of the release. The data comes in two formats, CSV and GeoPackage (GPKG).

• The GeoPackage format comes ready to load into the GIS package of the users choice with different gpkg files for each layer.

• The CSV format is more suited for loading into a database. It has all of the same layers in csv format and all the same attribution as the GeoPackage.

Data Enhancements

Land Cover information has been updated for Land, Road, Track or Path, Rail, Water and Structures Feature Types across OS NGD

These enhancements are supplied in a new cross-reference table that links to the Feature Types via the osid

The OS Land Cover classification has been mapped to EUNIS (European Nature Information System) & UK BAP (United Kingdom Biodiversity Action Plan) Broad Habitats classification schemes where possible

A percentage cover attribute has been added to the data and derived from machine learning and aerial imagery

Prior to March 2024 the following had also been achieved

• Improved consistency and accuracy to topographic area features in OS MasterMap Topography Layer and OS NGD

• Reduced number of descriptive terms per polygon.

• New minimum capture size specification for Rural and Moorland areas:

  Minimum area = 0.1 hectares (1,000m2)

  Minimum width = 5 metres

Land Cover enhancement

From March 2024 a series of habitat reference files are being made available for the OS NGD Feature Types containing Land Cover information:

• Land_habcoverref

• Structure_habcoverref

• Roadtrackorpath_habcoverref

• Rail_habcoverref

• Water_habcoverref

These link via the osid from the feature type polygons to OS Land Cover Tier B, EUNIS and UKBAP classifications in a one-to-many relationship. In the case here one osid has six lines in the reference file, one for each classification.

These cross-reference files come down by default when a customer orders any of the five feature types.

EUNIS is a tiered classification with Levels 1 and 2 allowing for customisable granularity from supergroups to individual species.

UK BAP is a mono-level categorisation scheme designed to put habitat types into groups based on their requirements and habitat formation.

In instances where there is no direct mapping between OS Land Cover Tier B classification and EUNIS Level 2 or UK BAP no percentage value is available

You can convert to UK HAB through the UK BAP classification scheme.

Table showing the different classifications for a single osid area

Percentage Land Cover

Each OS Land Cover Tier B value on the polygon (in this case Boulders, Mud, Shingle) is assigned a percentage value in the cross-reference table linked by the osid

The EUNIS and UK BAP Broad Habitat attributes are also given individual entries in the cross-reference table

Defined land cover classifications generally start at 10% and go up to 100%.

Where it has not been possible to match the machine learning classification to the classification of the topographic polygon, an 'Other' classification is added to the xref table to allow percentages to add up to 100% for a single polygon. (see Other at 30% in the image here). ‘Other’ classes can be as low as 5%

Only features above the Mean High Water line are given a percentage value

Percentages can be ‘null’ where a geometry or attribute change has occurred to the polygon area. These will be recalculated when the machine learning classification is next run.

Image showing the four OS Land Cover Tier B percentages in the Land_habcovref file for the osid highlighted

Attributes across the Land Cover enhancement layers

The five habcovref files all have the same attribution:

• osid

• scheme

• habitat code

• habitat description

• percentage

• percentage evidence date

• percentage update date

• feature type version date

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Links that may be useful:

OS NGD Documentation | OS National Geographic Databaseosngd.gitbook.io

OS Data HubOrdnanceSurvey

https://www.ordnancesurvey.co.uk/business-government/products/os-select-buildwww.ordnancesurvey.co.uk

This content has been developed from what was originally a Lightning Talk PowerPoint slide set. These slides are available to PSGA members to view and download from the PSGA members area of the OS website