> 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/how-field-boundary-data-is-created.md).
# How Field Boundary data is created
{% 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 %}
Diagram showing how Field Boundary data is created.
Field Boundary data is created by an automated process. The inputs to the process are OS NGD Structure 'Built Obstruction' Lines, OS aerial imagery (25cm), Digital Surface Model (DSM) and Digital Terrain Model (DTM).
1. After new imagery is available and the topographic area updates in 10km-by-10km areas are complete, the automated process is run to classify features and calculate height and width values.
2. Field Boundary features are coincident with and reference the underlying parent Structures ‘Built Obstruction’ Line. Field Boundary features follow the existing geometry of the Built Obstruction line.
3. Field Boundary features may be subdivisions of the Built Obstruction line where different classifications can be identified from OS aerial imagery. Where the line is not recognised as a vegetated or wall feature, the Field Boundary feature is classified as ‘Other’ (for example, fences, or newly planted hedges where features are too small to be identified from 25cm aerial imagery). Where the classification of Field Boundary features has not yet taken place by the automated process, these features are classified as ‘Unknown’.
4. Where more than one classification is present, the classification hierarchy is used to decide which classification should be applied, that is, Tree Canopy (highest) to Unknown (lowest). Any classified section of Field Boundary feature less than 4.0metres is ignored and subsumed into the surrounding classified sections based on the hierarchy.
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.
Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://docs.os.uk/osngd/using-os-ngd-data/os-ngd-structures/field-boundary/how-field-boundary-data-is-created.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
