OS NGD data is different from our other products because you access it from a single source where you'll find the data you need without having to download unnecessary datasets. It also has a simple data structure, designed to help you quickly answer questions and develop more intelligent solutions.

OS NGD terminology: themes, collections and feature types

Theme

A theme is a macro grouping of features which all represent similar geographic entities. Themes are the highest level of grouping within the OS NGD, and examples include ‘Buildings’ and ‘Transport’.

Themes allow for quick discovery and navigation when using OS Select+Build (the OS NGD download service) or the OS NGD APIs. They also give you the ability to quickly access all OS data relating to your particular theme of interest.

The nine OS NGD themes are: , , , , , , , , and .

Collection

A collection is a sub-grouping of the OS NGD themes. Collections group together similar types of data within a theme. Examples include ensuring network and routing data is separated from topographic features. For example, in the OS NGD Water Theme, there are two collections: OS NGD Water Features (topographic data) and OS NGD Water Network (network data).

This makes it easier for you to access only the data you require.

Feature type

A feature type is the most granular level of grouping within the OS NGD. Feature types have their own data model and specifications which are not commonly shared with other feature types.

When you order data through OS Select+Build (the OS NGD download service), the data you receive will be provided at a feature type level.

Who can access the OS NGD?

The OS NGD is available to OS Partners and to public sector organisations who are members of the Public Sector Geospatial Agreement (PSGA). OS Select+Build and the OS NGD APIs can be accessed via the on either the .

Data Exploration Licence

Alternatively, you can try out OS NGD collection data for free for three to six months by applying for . This licence is available for all collections apart from the Islands Address Collection.

The licence is primarily designed for organisations either considering becoming an OS Partner or who want to trial OS Premium data before working with an existing OS Partner.

How do you access the OS NGD?

The OS NGD is available via the on either the . There are three access methods to choose from once you are on the OS Data Hub:

• OS Select+Build: A download service which enables you to choose only the data you require and select how you want to receive your data.

• OS NGD API – Features: An OGC API – Features service.

• OS NGD API – Tiles: A vector tiles service based on OGC API – Tiles.

Introduction

The following pages provide an overview of the OS National Geographic Database (OS NGD); they cover the core elements of its design, including data formats, the coordinate reference systems used, and how Change-Only Updates (COUs) will be provided, amongst other topics:

Discover OS NGD

Detailed documentation on OS NGD design and practical guides on how to apply OS NGD data:

Explore OS NGD

In-depth information on OS NGD data, including structure, applications and news:

Get OS NGD

Try out OS NGD sample data, download it via OS Select+Build or access it through the OS NGD APIs:

Available formats for OS NGD data

OS NGD data is available in four easy-to-use formats: GeoPackage, CSV (comma-separated values), GeoJSON and vector tiles. The download service of OS Select+Build supports GeoPackage and CSV. OS NGD API – Features supports GeoJSON. OS NGD API – Tiles supports vector tiles.

CSV overview

CSV files are delimited text files which use commas to separate each attribute from the next. CSV is one of the file formats available via OS Select+Build. A single record is commonly provided per line, with a new line being started for each new record.

Geometry attribution will be provided as Well-Known Text (WKT).

CSV offers the following benefits:

• The single file is familiar to many customers and well used across GIS and data science tools.

• It is plug and play with most databases.

• The ability to quickly load large datasets using COPY method rather than INSERT.

CSV structure

The following table shows how different attribute types in the OS NGD are delivered when you choose to receive a CSV format. This includes whether to expect quotes, and how NULL values are treated.

GeoPackage overview

GeoPackage (GPKG) is an open standard data format as defined by the Open Geospatial Consortium (OGC). It is one of the file formats available via OS Select+Build. GeoPackage is designed to be a lightweight format that can contain large amounts of varied and complex data in a single, easy to distribute and ready to use file. Please be advised that older versions of GIS software may need updating before being able to display and interact with GeoPackage files.

GeoPackage offers the following benefits:

• The single file is easy to transfer and offers the end-user a rich experience.

• Attribute names are not limited in length, making it user-friendly.

• The file size limit is very large at 140TB, so lots of data can be easily accommodated (please note that a file size limit may be imposed by the file system to which the file is written).

GeoJSON overview

GeoJSON is an IETF standard designed to represent simple geographical features and their non-spatial attributes. It is used for encoding geographic data structures using JavaScript Object Notation (JSON). GeoJSON is used by OS NGD API – Features.

More information about the GeoJSON IETF standard can be found .

Supported geometry types:

• Point

• LineString

• Polygon

Vector tiles overview

Vector tiles are clipped tiles, or grid squares, composed of layers of vector features which are optimised for caching, scaling and producing map imagery quickly. They serve in a similar way to raster tiles but have the added functionality of being customisable by users. A client application requests tiles based on a zoom level and extent, and the server responds with binary data representing the vector tiles containing the layers to be visualised on that map.

OS NGD API – Tiles serves vector tiles as raw information which is presented using compressed packets of geographic data using the Protocolbuffer Binary Format (.pbf).

Vector tiles offer the following benefits:

• User customisation and styling functionality – customise your map with full and dynamic design control.

• Small file size – lightweight tiles that are efficient and quick to render in your client application.

• Pixel perfect maps – high-resolution, beautiful mapping for all devices (web and mobile devices).

File naming

When you place an order for OS NGD data via OS Select+Build, the following file naming convention will be applied to the data you receive:

themeshortcode_collectionshortcode_featuretype

In order to keep file names manageable and not overly long, shortened file names ('short codes') have been used for both the theme and collection. Using short codes in our naming convention also ensures we have consistency in naming between OS Select+Build and the OS NGD APIs.

An example of how these short codes are used is below, with the example showing a file name which would be created for an order of the Built Address Feature Type within the OS NGD GB Address Collection of the OS NGD Address Theme:

add_gb_builtaddress

A full list of the short codes we use in OS Select+Build and the OS NGD APIs is detailed in the following table:

Unique identifiers in the OS NGD

OSID

The OS NGD primarily uses an identifier called the OSID (OS Identifier). OSIDs uniquely identify records within a feature type and have a maintained lifecycle, enabling them to support change tracking and linkages across datasets.

It should be noted that while an OSID is unique within a feature type, it may be shared across feature types when they represent the same real-world feature. For example, a point feature in the OS NGD Geographical Names Theme representing a water body will share the same OSID as the water body feature in the OS NGD Water Theme.

UPRN, USRN, UDPRN and postcode

Other unique identifiers are also present in the OS NGD, including:

• UPRN (Unique Property Reference Number) for Local Authority Address records.

• USRN (Unique Street Reference Number) for Local Authority Street records.

• UDPRN (Unique Delivery Point Reference Number) for Royal Mail delivery points (for example, a mailbox or business unit).

These unique identifiers remain the authoritative identifiers for their respective domains.

🆕 Feature ID

For a small number of feature types in OS NGD where it is not possible or necessary to have identifiers that persist over time, the Feature ID is used as the primary unique identifier. The , , and Feature Types use this unique identifier. The notional extents of the retail area features and Postcode Unit Area features are regenerated periodically (for example, monthly for the latter), at which point all features will get a new Feature ID.

Other identifiers provided in the OS NGD

TOID

The Topographic Identifier (TOID) is also present in the OS NGD, primarily to support customer migration from OS MasterMap products to the OS NGD. This is an optional attribute and should not be relied upon to complete data linking or for implementing Change-Only Updates (COUs). The reason for this identifier being optional is the improved currency on which the OS NGD is published, meaning the TOID, which is created in our existing OS product systems, will not always be allocated to features as frequently as they will be accessible via the OS NGD.

On the feature type pages (which are located in the Data Structure section), the following information can be found about each attribute:

• Name and Definition: The name of the attribute and what it is describing.

• Data Types: The values the attribute can take. For example, a numeric value or a string. This is provided for all three data formats – GeoJSON, GeoPackage, and CSV.

• Nullable: A True or False value to denote whether the attribute always has to be populated with a value (False) or can be NULL (True).

• Code List Name: The name of the code list used in association with the attribute (if applicable) and a hyperlink to the page displaying that code list.

• Max Length: Values are given here to indicate the maximum length that you will find in the attribute, to aid in developing applications.

• Multiplicity: Describes how many times this value is expected to be populated in the data. These values may be used in combination.

  • 1: There must be a value.

  • 2: There must be two values.

• OS NGD API – Features Filterable: A Yes / No value to denote whether you can refine your query in OS NGD API – Features specifically on this attribute.

• OS Select+Build Filterable: A Yes / No value to denote whether you can refine your order in OS Select+Build on this attribute.

• Data Schema Version: The OS NGD schema version the data above applies to. Please note that concurrent schema versions may be available at one time. For more information on how data schema versioning works in the OS NGD, please refer to the .

Through the OS NGD, Ordnance Survey aims to iterate and release data enhancements quicker than ever before. We want to be able to do this without disrupting customers who have adopted data schemas and are heavily reliant on a specification remaining the same for a longer period of time. With this in mind, the OS NGD is able to run multiple data schema versions for a single feature type at any given time.

When we release a new data schema version in the OS NGD, the changes will be visible on the feature type pages of this documentation platform. As you can see from the image below, each attribute on a feature type page states which data schema version it is present within, with the Version Date attribute in the example below being present in both data schema versions 1.0 and 2.0:

Change-Only Updates (COUs) are only available for CSV data supplies of the OS NGD. The benefit of taking COU supplies is that you only receive the features which have changed since your last supply, reducing the overall size of the files you receive.

There are some restrictions on when you can choose to take COUs; these restrictions are dependent on the selections you make when ordering OS NGD data. Please see the 'Data ordering and currency' page for more information.

Upon OS NGD launch, if you choose to receive a COU supply for your CSV data, this can be provided on either a daily or monthly frequency. In both cases, your COU file will contain any changes which have been made to the underlying data within the selected time frequency. If no changes have been made to a selected feature type of your choice, then you will receive a blank COU file.

The key attribution required to use and implement a COU is detailed below:

• Unique Identifier: The unique identifier for the feature type you are using is how you will ensure you are updating the correct records in your data holdings. In most instances the unique identifier will be the OSID, but this is not always true, therefore please check the appropriate feature type pages in our documentation.

• Version Date: This is the date when the feature was last updated in OS product databases.

• Version Available From Date: This is the date when the feature became the latest version and was published to customers.

• Version Available To Date: This is the date when the feature was superseded by an update or ceased to exist.

• Change Type: This is a code list which gives more information about the type of change which has occurred.

OS Select+Build

The GeoPackage and CSV formats accessible via OS Select+Build are available in four different coordinate reference systems dependent on your selection:

• British National Grid (BNG: EPSG: 27700)

• British National Grid + ODN Height (EPSG: 7405)

• European Terrestrial Reference System (ETRS89: EPSG: 4258)

• World Geodetic System (WGS84: EPSG: 4326)

Default coordinate reference systems for OS Select+Build

The following table outlines the default coordinate reference system used by each OS NGD collection in OS Select+Build:

Selecting a coordinate reference system

When (the bespoke download service for OS NGD), you can choose what coordinate reference system you'd like to receive the data in.

If you don't choose a particular coordinate reference system for your data package, OS Select+Build will automatically select the default coordinate reference systems for the feature types in your data package for you.

OS NGD APIs

OS NGD API – Features

The GeoJSON format accessible via OS NGD API – Features is available in four different coordinate reference systems:

• British National Grid (BNG: EPSG: 27700).

• World Geodetic System (WGS84: EPSG: 4326)

• British National Grid + ODN Height (EPSG: 7405)

OS NGD API – Tiles

The vector tiles format accessible via OS NGD API – Tiles is available in two different coordinate reference systems:

• British National Grid (BNG: EPSG: 27700)

• Web Mercator (EPSG: 3857)

Definitions for the coordinate reference systems available in the OS NGD

To get access to the OS NGD you must first log into the OS Data Hub. The OS NGD is accessible via both the Premium Plan and Public Sector Plan on the OS Data Hub.

Geographic filtering

There are three options within OS Select+Build (the OS NGD download service) in relation to the geographic extent of your order. These are:

• Great Britain: Receive all data for the whole of Great Britain.

• Customer Specified Area: Draw an area of interest (AOI) and only receive the data which intersects this area.

• Pre-defined Area: Select a pre-defined area, and only receive the data which intersects this area.

Order update options

When accessing the OS NGD, the following order update options will be available:

• One Off Full Supply

• Regular Full Supply

• Change-Only Update (COU; after an initial Full Supply)

The following frequencies will be available dependent on the type of order you place:

• Daily Supply: This will provide you with the latest updates OS have loaded and verified for publication since the previous day as a COU file.

• Monthly Supply: Either a Full Supply or COU Supply of all the changes which have occurred in the previous month.

• Annual Supply: A Full Supply of the data to show how the data looked at the end of each year.

Further details about the options available to you can be found further down on this page.

Update files

If you choose to receive a COU supply for your CSV data, this can be provided on either a daily or monthly frequency. In both cases, your COU file will contain any changes which have been made to the underlying data within the selected time frequency. If no changes have been made to a selected feature type of your choice, then you will receive a blank COU file.

File supply

If you use OS Select+Build to access the OS NGD, then a separate download file will be provided for each feature type you order. For example, if your selected theme has two feature types you will be supplied with two separate files (CSV or GeoPackage) as part of your order.

Ordering combinations

The following tables summarise the different options available to you dependent on what you specify when ordering your data through OS Select+Build.

For the purposes of the tables below, the following definitions are being used:

• Unfiltered means a Great Britain supply with no further attribute filters applied.

• Filtered means an order for data which either has a geographic filter applied or an attribute filter applied.

GPKG files

CSV files

Order Summary File

Feature types downloaded via OS Select+Build will be supplied with an Order Summary File, a small JSON manifest that provides key metadata about the supplied file. You can use this file to validate the data to ensure the currency, record count, schema version, feature name and coordinate reference system (CRS) match your expected order.

The following file naming convention will be applied to each Order Summary File you receive:

• collection_featuretype_orderSummary.json

For example, the file name for the Building Part Feature Type Order Summary File would look like this:

• bld_fts_buildingline_orderSummary.json

The example below shows the information an Order Summary File contains:

The following table provides a brief description of each field:

Currency of OS NGD data

OS Select+Build and OS NGD API – Features

Whether accessing OS NGD data through OS Select+Build or OS NGD API – Features, the following currency of the data will apply:

For collections that are not updated daily, the table below provides the date of the last update; it also shows the version of the OS MasterMap product to which the OS NGD data corresponds, if applicable:

OS NGD API – Tiles

When accessing OS NGD data through OS NGD API – Tiles, the data currency is weekly for the basemap and variable for the four data overlays – please see the for more information on update frequency, available feature types and available attribution for this API.

Feature counts for the OS NGD Transport Theme

Feature counts are detailed below for the and Collections of the . These feature counts will be updated monthly to reflect data currency for these collections.