Field Boundaries

A Lightning Talk

What are the Field Boundaries?

Field Boundary

These are line features in the Structures Collection with geometry matching with the obstructing features demarking field boundaries outside of urban areas, as found in Structure Line of the Structures Collection.

Identification of the nature of the field boundary feature when adjacent to agricultural land, forestry, rough grassland or heath, and whether the field boundary is vegetated or a wall.

What formats does the OS NGD data come in?

The OS NGD Field Boundary 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, however instead of storing the geometry in a GIS ready format, it is stored as a POLYGON, POINT or LINESTRING attribute with all of the vertices stored as co-ordinate pairs in the text file.

What is the attribution?

The attribution varies between the feature types, but there are some common features:

• All OS NGD data has an OSID, version info and changetype

• Link to the structure line features within the OS NGD structure theme using the Structureline OSID as the unique identifier.

• The data now has geometry evidence and update dates so users can see when the information was updated

• Information on the type of field boundaries, can be found in the description

• Details of the size of the boundaries will be available for the vegetated boundaries.

• A flag will be included indicating if the line segment represents part of a woodland boundary.

Field Boundaries themed by Description with attribution

How the data is created

Field Boundary features are classified where there are existing ‘built obstruction’ structure lines adjacent to, or contained within, areas of Agricultural Land, Trees, Rough Grassland or Heath. Includes field boundary features adjacent to land in the Rural Payments Agency (RPA) Rural Land Register (RLR) where they are in urban areas in England

Examples of the 6 Field Boundary Types in OS NGD Structures

Structure OSID

The field boundary data segments the geometry of the built_obstruction lines.

However, each field boundary segment holds a Structure OSID that can be used to link back to the original OS NGD structure line.

The relationship between Structure OSID and the OS NGD Structure Line

Field Boundaries Description

The classification will follow the hierarchy from the previous image, resulting from using aerial imagery to determine it.

For example, a wall at the edge of a forested area will be classified as a tree canopy as it would not be possible to see the wall beneath the canopy in imagery

• Tree Canopy is defined as instances of vegetation canopy

• Wooded Strip is defined as a continuous row of trees.

• Hedges are defined as a row of shrubs.

• Wall made with stones that fit together firmly with or without mortar

• Other is where a classification has not conclusively identified the Field Boundary as a hedge or tree or wall. Fences will fall under this classification.

• Unknown is where a geometry edit to the OS NGD Obstructing Line has occurred outside of the cyclical revision process. This will be completed from the next cyclical revision epoch.

Field Boundary Height, Width and Length

Height, width and length, derived from imagery. sizes are to provide an indication of height & width, rather than an absolute value.

Classification	Height (min/max)	Width (min/max)	Length (min/max)
Tree Canopy	3.5m/no max	0.5m/20.0m	4.0m/49.9m
Wooded Strip	3.5m/no max	0.5m/20.0m	50.0m/no max
Hedge	0.5m/3.5m	0.5m/20.0m	4.0m/no max
Wall	n/a	n/a	4.0m/no max

Use Cases for Field Boundaries

Following Engagement with the community the following use cases for the data were captured

• Flood risk assessment to understand where boundary features can hold back water.

• Design and administration of agricultural farming payments.

• Vegetated boundaries are an important habitat to map, monitor natural capital and to link to existing services and national statistics.

• Understanding surface runoff into watercourses, assessing the impact of this and mitigating the effect

• Hedges are a high priority habitat type which provide a pollinator network, so it is important to understand their location, habitat networks and connectivity.

• Development of Environmental Land Management Schemes to achieve local based environmental outcomes.

• Understand hedgerow decline over time and biodiversity loss as these are a priority habitat.

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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