> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/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/os-downloads/products/maps-and-imagery-portfolio/os-vectormap-district/os-vectormap-district-overview/generalisation.md). # Generalisation The detail within OS VectorMap District has been generalised from Ordnance Survey large-scale data. Map generalisation is the process of reducing the scale and complexity of map detail whilst maintaining the important elements and characteristics of the location. Map generalisation comprises of the following processes: * **Selection/omission:** Some features that appear at larger scales are not selected at the smaller scales. For example, in the public amenities layer individual features in close proximity can be grouped to a single point. * **Simplification:** Simplification can take a number of forms in OS VectorMap District. It can be line simplification, for example, in a vector product; a very winding stream could have the number of data points that represent it reduced. * **Exaggeration:** Features that are small but are too important to a particular landscape to be omitted are enlarged. For example, some isolated rural buildings are often enlarged to a minimum size rather than being omitted. * **Aggregation:** Aggregation is the combining of a number of small features to make a larger one, such as buildings. * **Symbolisation:** Features that are shown in detail in other OS products, such as OS VectorMap Local may be shown by standard symbolisation in OS VectorMap District. For example, railway stations are depicted as point symbols. * **Displacement:** The movement of the representation of a feature away from its ground position in order to maintain its prominence. There is very little displacement in OS VectorMap District, but in certain circumstances, some features may be moved away from adjacent detail if their representation would otherwise be lost; for example, some buildings are moved away from road edges to ensure they remain prominent. --- # 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 dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.os.uk/os-downloads/products/maps-and-imagery-portfolio/os-vectormap-district/os-vectormap-district-overview/generalisation.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. 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.