> For the complete documentation index, see [llms.txt](https://docs.os.uk/more-than-maps/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/more-than-maps/data-demonstrators/topography-demonstrators/os-mastermap-r-demonstrators/os-mastermap-topography-layer.md). # OS MasterMap Topography Layer A Lightning Talk ## OS MasterMap Topography Overview

Image of OS MasterMap Topography Layer representing part of Exeter — OS MasterMap Topography Layer

OS MasterMap Topography Layer is a digital data product made up of real world fixed features such as fields, roads and buildings, as one continuous dataset. With OS MasterMap Topography Layer, each feature is a record, which has information about the feature’s position and shape on Earth – its geometry – as well as details about it - ‘attributes’ - which provide metadata describing the feature, such as it's make e.g. man-made or natural, and it's description e.g. building or road. OS MasterMap Topography Layer provides an accurate visual context to help interpret addresses, routes and imagery provided by the other OS MasterMap layers.

Diagram showing the OS MasterMap Topography Layer in the context of the OS MasterMap family of products. It shows the product family including Topography Layer, Water Network, Sites Layer, Greenspace Layer and Highways Network. — OS MasterMap family of products structure

The product's primary purpose is to provide the most detailed topographic data available of the physical environment of Great Britain. OS MasterMap Topography Layer is published every 6 weeks to a consistently high standard, regularly updated by ground and aerial survey. ### Key Characteristics The key characteristics and benefits of OS MasterMap Topography Layer are: * Each uniquely referenced feature has attribution that provides information about the real-world object it represents and metadata that tracks changes to the feature’s lifecycle. (Metadata is data that provides information about the data). This means you can track a feature over time. As well as being able to see what has changed, you can understand more about features, such as when it was last changed, the reason for change, its description and make - whether it is a manmade or a natural feature. * OS MasterMap is presented seamlessly with 500 million real world objects – all uniquely identified. * The product employs a scale of data capture appropriate to the density of features – the higher the number of features within an area, the larger the scale used to survey them – ensuring the detail of individual features can be shown. Coordinates are delivered in British National Grid (with the exception of Vector Tiles format, which is supplied in Web Mercator projection – EPSG:3857). * OS MasterMap Topography Layer can be used as part of a data modelling or a predictive modelling tool (predicting future events or patterns). An example of predictive modelling is mapping crime; analysing the type of areas crime is occurring in and then using the results to find similar areas where crime could occur. * In addition, OS MasterMap Topography Layer is also used by organisations looking for areas where specific physical conditions exist. A retailer, for example, may use OS MasterMap Topography Layer to help them find a site for a new store by using the attribution to find land parcels of a certain size and distance. Emergency planners may use OS MasterMap Topography Layer to assist in planning and preparing for emergencies by identifying the areas most likely to be affected. The product can be used to map or model the sequence of events in any given type of emergency, so that emergency services' own resources and command centres are unlikely to be cut off or taken out of action by the emergency itself. Individual real-world topographic features in the OS MasterMap Topography Layer are represented by polygons (closed objects), lines, and points , each with their own unique reference, called a topographic identifier (TOID). Each feature has one of these three geometrical structures – polygon, lines and points. Polygon features fit seamlessly with each other topologically within structuring layers. {% tabs %} {% tab title="Polygons" %}

Image of OS MasterMap Topography Layer representing part of Exeter, showing only polygon features. — Polygon features in OS MasterMap Topography Layer

This view shows polygon features; buildings, road casings, land (both manmade and natural). {% endtab %} {% tab title="Lines" %}

Image of OS MasterMap Topography Layer representing part of Exeter, showing line features as grey lines on a white background. — Line features in OS MasterMap Topography Layer

This view shows lines, depicting the outlines of buildings, the edges of roads, junctions, pavement and paths. {% endtab %} {% tab title="Points" %}

Image of OS MasterMap Topography Layer representing part of Exeter, showing point features as grey points on a white background. — Point features in OS MasterMap Topography Layer

This view shows points such as spot heights, position of individual trees, posts, heritage features and masts. {% endtab %} {% tab title="Cartographic Text" %}

Image of OS MasterMap Topography Layer representing part of Exeter, showing grey cartographic text features on a white background. — Cartographic Text features in OS MasterMap Topography Layer

This view shows cartographic text in OS MasterMap Topography Layer. This text adds information to the data when displayed as a map including road and place names. {% endtab %} {% tab title="Combined View" %}

The final view is of all the different feature types combined for the centre of Exeter, as cartographic representation of the real world. {% endtab %} {% endtabs %} ### Area features represent real world objects OS MasterMap Topography Layer shows real world features on the ground such as buildings, roads, and paths. The term 'real-world object' is used to describe a geographic entity that can be captured and represented in the data (e.g. anything fixed on the ground that you can trip over or walk into). The data is captured by Ordnance Survey surveyors using GPS surveys on the ground and by aerial imagery. For cartographic representation, OS MasterMap Topography Layer is captured and designed for display at 1:1250 Urban, 1:2500 Rural and 1:10 000 Mountain and Moorland scales for urban, rural and mountain and moorland areas respectively. In Geographical Information Systems (GIS), OS MasterMap Topography Layer can be viewed over a range of scales. The most scale-sensitive feature types, such as cartographic text and symbol features, are fixed in size and rapidly become less clear at smaller display scales (that is, when zoomed further out to see a larger geographic area). OS MasterMap Topography Layer is also suitable for use in non–cartographic applications where the concept of scale is less applicable. ### Polygon Closing Links / Inferred Links OS MasterMap Topography Layer includes both closing and inferred links. These are line features which are created in the data to show actual boundaries for features on the ground which are not visible in the real world. They are lines that Ordnance Survey has introduced into the data to make some types of polygons into more manageable units. There are three main types. {% tabs %} {% tab title="Network Closing Links" %}

Network closing links as shown in OS MasterMap Topography Layer. The links appear as dashed red lines on a pale basemap. — Example of network closing links in OS MasterMap Topography Layer

The first type are network closing links. These are frequently found where roads meet at junctions. They are described as Polygon Closing Link under Descriptive Term. {% endtab %} {% tab title="Inferred Property Closing Links" %}

Inferred property closing links as shown in OS MasterMap Topography Layer. The links appear as dashed red lines on a pale basemap. — Example of inferred property closing links in OS MasterMap Topography Layer

Another example is the creation of a link to separate an open-plan garden around a pair of semi-detached houses into two distinct entities, reflecting that there are two properties there in the real world. They are described as Inferred Property Closing Link under Descriptive Term. {% endtab %} {% tab title="Divisions" %}

Example of division features in OS MasterMap Topography Layer

The third type are closing links between properties such as semi-detached. They do not constitute the legal boundary of any property any more than a physical line feature does. These links are clearly identified in the ‘descriptive group’ attribution and if a customer wishes to not show these features that is possible. They are described as Division under Descriptive Term. {% endtab %} {% endtabs %} ## Themes within OS MasterMap Topography Layer A *Theme* is a set of features that have been grouped together and provide a means of dividing the data in a logical and user-friendly fashion. A feature can be a member of any number of themes but must belong to at least one theme as a minimum requirement. The themes are: * Administrative Boundaries * Buildings * Heritage and Antiquities * Land * Rail * Roads Tracks, and Paths * Structures * Terrain and Height * Water ### Administrative Boundaries Administrative boundaries are defined as showing the limits of responsibility and representation for electoral and administrative purposes. Boundary alignments are shown within the Administrative Boundaries theme. As well as the boundary’s relationship to real-world objects, its boundary descriptions, where needed for clarification, are also supplied.

Boundary theme features in OS MasterMap Topography Layer. The features appear as purple dashed lines on a pale basemap — Administrative boundaries theme features with OS Maps API for background context.

Boundary theme features in OS MasterMap Topography Layer with an inset box showing attribution. The features appear as purple dashed lines on a pale basemap — Attributes for an individual feature in the administrative boundaries theme.

### Buildings Buildings are defined as permanent roofed constructions, usually with walls. This includes permanent roofed constructions that exceed 8.0m² in area (12.0m² in private gardens). Exceptions are made to this area rule for smaller buildings that, due to their detached position, form relatively important topographic features; these are shown at minimum size, as stated above.

Building theme features in OS MasterMap Topography Layer. The features appear as brown polygons with black text labels on a pale basemap. — Buildings theme features with the OS Maps API as a backdrop giving context.

Building theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted building feature appears as a red polygon. — Attributes for an individual feature in the buildings theme.

### Heritage and Antiquities Heritage and Antiquities are defined as existing artificial features of a date not later than AD 1714 (the date of the accession of George I). This can refer to individual points or objects in the data. These antiquities are captured along with very important battlefield sites and natural features connected with important historic events.

Heritage and Antiquities theme features in OS MasterMap Topography Layer. The features appear as grey line and point features with grey cartographic text on a pale basemap. — Heritage and antiquities features with the OS Maps API as a backdrop giving context.

Heritage and Antiquities features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted feature appears as a red polygon. — Attributes for an individual feature in the heritage and antiquities theme.

### Land A land feature is defined as either a man-made or a natural polygon feature that describes the surface cover and area to which it is applied. This includes both natural and man-made slopes and cliffs. All general features are also placed in the Land theme. There are some exceptions to this, such as routes of communication and buildings.

Land theme features in OS MasterMap Topography Layer. The features appear as green polygons with black text labels on a pale basemap. — Land features with the OS Maps API as a backdrop giving context.

Land theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted land feature appears as a red polygon. — Attributes for an individual feature in the land theme.

### Rail Rail features are defined as features related to travel by railway or tramway. The exception to this is railway tunnels, which are currently in the Structures theme. OS MasterMap Topography Layer contains information relating to permanent railways that form the network between two points. Examples include the track from railway station to railway station, or the track from an industrial building to a private quarry.

Rail theme features in OS MasterMap Topography Layer. The features appear as grey polygons on a pale basemap. — Rail features with the OS Maps API as a backdrop giving context.

Rail theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted rail feature appears as a red polygon. — Attributes for an individual feature in the rail theme.

### Roads, Tracks, and Paths Road: A road is defined as a metalled way for vehicles. Roads that form part of the public network and driveways to private properties that are over 100m in length are normally included within OS MasterMap Topography Layer Track: A track is defined as an unmetalled way that is clearly marked, permanent and used by vehicles. Tracks are only normally recorded in private gardens if they are 100m or more in length. They need not be ‘all weather’. Paths: A path is defined as any established way other than a road or track. They can be considered as either ‘made’ or ‘unmade’.

Roads tracks and paths theme features in OS MasterMap Topography Layer. The features appear as grey polygons on a pale basemap. — Roads, tracks and paths features with the OS Maps API as a backdrop giving context.

Roads tracks and paths theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted road feature appears as a red polygon. — Attributes for an individual feature in the roads, tracks and path theme.

### Structures Structures are defined as features that are man-made constructions but do not qualify as buildings, for example, Band Stands and Clock Towers. These features may or may not obstruct passage at ground level. OS MasterMap Topography Layer contains information relating to all permanent structures that are considered large enough to be included (minimum area of 4m squared) - if they are not captured they might be shown by text. Structures include stand-alone monuments, fountains, covered reservoirs, pylons, weirs and sluices, gas holders, pontoons, and uncovered tanks.

Structures theme features in OS MasterMap Topography Layer. The features appear as grey polygons on a pale basemap. — Structures features with the OS Maps API as a backdrop giving context.

Structures theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted structure feature appears as a red polygon. — Attributes for an individual feature in the structures theme.

### Terrain and Height These features denote the ground level at any given point. OS MasterMap Topography Layer does not contain height contours; instead it contains height information point features of known height.

Terrain and height theme features in OS MasterMap Topography Layer. The features appear as grey crosses with grey text denoting a height on a pale basemap. — Terrain and height features with the OS Maps API as a backdrop giving context.

Terrain and height theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted spot height feature appears as a red point. — Attributes for an individual feature in the terrain and height theme.

### Water Water features are defined as features that contain, delimit, or relate to real-world objects containing water. Examples include streams, lakes, rivers, tide lines and canals.

Water theme features in OS MasterMap Topography Layer. The features appear as blue polygons on a pale basemap. — Water features with the OS Maps API as a backdrop giving context.

Water theme features in OS MasterMap Topography Layer with an inset box showing attribution. The highlighted water feature appears as a red polygon. — Attributes for an individual feature in the water theme.

## Example Use Case A local authority could use the OS MasterMap Topography Layer to maintain a register of land and buildings in their ownership. They can attach their own attribution to that already provided with the product. When this kind of data association takes place, it can lead to efficiencies in storing and using data. It can also enable data to be shared more easily both between and within organisations. One example use case of the data is by Transport for the West Midlands (TfWM) who have used OS MasterMap Topography Layer to build a transport network layer. This project allowed Transport for West Midlands to work more efficiently, saving them time and money, reducing site visits, and significantly improving decision making. The project enabled Transport for West Midlands to use Ordnance Survey data products to understand the geography of their network for road space reallocation, active travel planning, and other transport planning schemes such as emergency vehicle routing.

A representation of the road network as used in the TfWM project. Roads are represented as pink line features on a pale basemap. — The road network used in the project

The project used the topology of the roads layer as the actual road dimensions were one of the key elements TfWM were interested in. The methodologies that they developed enabled the identification of detailed street scenes with widths at one metre internals based on the road polygons. This provided a better understanding of the road space available and differing street gradients were highlighted to show the optimal locations for mobility hubs. The methodologies developed will be supporting future TfWM projects in numerous ways - from identifying detailed street scene widths, to understanding available the road space. ## Product Supply The available formats for the product are: • GeoPackage • Vector tiles (MBTiles) (National cover full supply only) • Geography Markup Language (GML) 2.1.2 4.2 File sizes vary greatly depending on tile size and the quantity of features present in a tile:

Table describing typical file sizes for OS MasterMap Topography Layer

### Ordering OS MasterMap Topography Layer OS MasterMap Topography Layer is obtained from a web-based ordering system that allows users to order an initial data supply and set a schedule for updates as required. The product is supplied as an online download from the [OS Data Hub](https://osdatahub.os.uk/), and is available in the following formats: • GeoPackage (for area of interest only) • Vector tiles (MBTiles) (National cover only) • Geography Markup Language (GML) version 2.1.2 The GML download ZIP package contains a GZ (.gz) file, which does not require extraction and contains multiple GML (.gml) files. The GML data is supplied in 5km ² tiles and features are not clipped at the tile edges, resulting in what is called “hairy” tiles. The DataHub also has two options for ordering the data: * 5km downloads as either national cover or an area of interest. * National coverage (all of Great Britain). ### Feature Validation Dataset The Feature Validation Dataset (FVDS) is a set of files that can optionally be supplied with either a Full Supply Change Only Update (COU) or an Area of Interest (AOI) COU of an OS MasterMap Topography Layer order in GML format only. The FVDS allows the validation of the data holding ensuring it contains the correct set of features after loading. It does this by reporting on all the data it expects to find in the holding after the application of the supply, not just what is contained in the supply. The FVDS is intended to be used for periodic checks on data holdings maintained by a COU regime. It can also be used to check that an initial supply of OS MasterMap Topography Layer data has been correctly loaded. The FVDS can be used with both geographic and non-geographic chunk file options. The FVDS is a comma-separated value (.csv) text file format that gives the TOID, version number and version date of every feature that should exist in the current data holding, based on the polygon extent, themes, polygon format and extraction date of the current order. ### Change only update When you order the product you can decide to receive: * A one off supply of your area of interest. * Or a complete resupply of the whole product to replace the data in your current holdings. * Or an initial supply with a change only update schedule or just the changes in area (change only update). The frequency for change-only-update is six weekly. If Geo Chunks are requested the change file will include inserts. OS Products refresh dates can be found [here](https://docs.os.uk/os-downloads/resources/product-resources/product-refresh-dates). The below series of images shows the change over time in area between different data releases and how change only update can show visually change in an area overtime. {% tabs %} {% tab title="2010" %}

OS MasterMap Topography Layer representation of an area of Southampton in 2010. Buildings appear as beige polygons, roads as grey polygons, water as blue polygons, and land as green and brown polygons. — OSMM Topography Layer representation of a particular area in 2010

{% endtab %} {% tab title="2015" %}

{% endtab %} {% tab title="2023" %}

{% endtab %} {% endtabs %} Using change only update is useful in helping to monitor change over time in an area. By comparing different versions of the data, users can analyse how landscapes and structures have evolved. The use of change only update helps with the creation of historical views. What did a particular area look like before a new development, how might this affect the local environment? What was there before a new development? Was the development built on a green field site? Where did roads go before a development? ## Styling To optimise the cartographic representation of the data, there are four different styles available: Standard, Road, Outdoor and Light. These predefined stylesheets are available in four formats (QGIS QML files, ESRI Layer files, Style Layer Descriptor (SLD) and JSON) for interoperability with GIS and web map services. The files can be downloaded via the 'OS MasterMap Topography Layer Stylesheets page' on [GitHub](https://github.com/OrdnanceSurvey/OSMM-Topography-Layer-stylesheets). Note: Click the 'Code' drop-down button and then click 'Download ZIP' to access the styling files from GitHub. See [here](https://docs.os.uk/more-than-maps/geographic-data-visualisation/geodataviz-assets/styling-data/how-to-download-and-use-os-stylesheets) for a guide on downloading and using OS style sheets. The following images are examples of the four different styles for OS MasterMap Topography Layer. {% tabs %} {% tab title="Standard" %}

OS MasterMap Topography Layer representation of an area in the standard styling. Buildings appear as beige polygons, roads as grey polygons, water as blue polygons, and land as green and brown polygons. — Standard OS MasterMap Topography Layer style

This is the original style which was created when OS MasterMap was first released. {% endtab %} {% tab title="Road" %}

OS MasterMap Topography Layer representation of an area in the road styling. Buildings appear as beige polygons, roads as white polygons, water as blue polygons, and land as green and brown polygons. — Road OS MasterMap Topography Layer style

A familiar style with a focus on transport networks - specifically highlighting the Great British road network. High in contrast with lots of detail and colour. {% endtab %} {% tab title="Outdoor" %}

OS MasterMap Topography Layer representation of an area in the outdoor styling. Buildings appear as beige polygons, roads as white polygons, water as blue polygons, and land as green and brown polygons with symbols. — Outdoor OS MasterMap Topography Layer style

This style focuses on terrain and land cover, it has a minimal colour palette and familiar symbology. Useful as an overview of an area and clearly shows different feature types, making it particularly useful for rural areas. {% endtab %} {% tab title="Light" %}

OS MasterMap Topography Layer representation of an area in the light styling. Compared to other styles, the colours are muted. — Light OS MasterMap Topography Layer style

Designed specifically for data visualisation, this style has a subtle palette and is simple and clear. Use it to add geographic context. It is ideal for when you want to add additional layers on top of the data but still want to view the underlying features. {% endtab %} {% endtabs %} ## OS MasterMap Building Heights OS MasterMap Topography Layer – Building Height Attribute is a dataset containing absolute and relative height values for buildings and selected structures contained within OS MasterMap Topography Layer. It is an enhancement to, and forms part of, OS MasterMap Topography Layer. Building Height Attribute contains height values for buildings, tanks, chimneys (industrial) and glasshouses, specifically for Topographic Area features with the theme of ‘Buildings’ within OS MasterMap Topography Layer.

A 3D representation of a built up area where water is represented in blue, roads in white, land in brown and green, and buildings as 3D brown objects of varying heights — 3D representation of buildings

### Product Supply Building Height Attribute data is supplied in an uncompressed comma-separated values (CSV) file format, which can be downloaded from the [OS Data Hub](https://osdatahub.os.uk/). Building Height Attribute is supplied in 5km² geographic chunks. Each 5km² chunk will contain Building Height Attribute values for any building polygon that intersects that area. As such, any Building Height Attribute values that fall across tile boundaries in contiguous tiles will be duplicated. Tiles are supplied with all available data contained within them. Not all 5km² tiles will have complete coverage. ### How to use it To use use Building Heights, join the Building Height Attribute data to the corresponding OS MasterMap Topography Layer feature by linking the Building Height attribute to the building topographic identifier (TOID) in OS MasterMap. An OS MasterMap Topography Layer licence is required to use the Building Height Attribute data and provides full national coverage. ### How OS MasterMap Height data is created Building Height Attribute data is generated from photogrammetrically derived Digital Terrain Models (DTMs) and Digital Surface Models (DSMs). That is, information gathered from aerial surveys as part of Ordnance Survey's cyclical revision programmes. DTMs show the bare ground surface, having extruded features such as buildings, trees, etc, whereas DSMs depict the elevations of the top surfaces of buildings, trees, towers and other features elevated above the bare earth.

Diagram showing the difference between a DTM and DSM. A DTM represents the height of the ground and a DSM additionally represents the height of objects on the ground e.g. buildings and trees. — Diagram of a DTM and DSM

### Attribution

#### Absolute Height Minimum (AbsHMin) The lowest point extracted from the DTM (digital terrain model) within the footprint of the building as represented in OS MasterMap Topography Layer. This aims to represent the lowest absolute height of the intersection of the external building walls and the underlying ground surface. #### Absolute Height Maximum (AbsHMax) This represents the highest point of the building extracted from the DSM (digital surface model) within the footprint of the building or structure represented in OS MasterMap Topography Layer. The highest point could be represented by any structure on top of the building, provided it is of sufficient size to be captured in the DSM source data. This may include industrial chimney stacks, machinery and any substantial structures that may be present on top of the building. Smaller structures like chimney stacks as found on residential buildings will be excluded from the AbsHMax measurement. #### Absolute Height 2 (AbsH2) AbsH2 is a calculated value which aims to represent the lowest point where the roof intersects the alignment of the external vertical walls of the principal part of the building. This is usually referred to as the building eave height. The principal part of the building is defined as the main structure, excluding elements at higher or lower elevation. In buildings with multiple heights (for example, a main two storey building with a smaller single storey extension), the eave height is calculated from the largest building extent. #### Relative height values The two relative building height values are generated from the differences between the absolute elevation values. The relative heights can be used in isolation to provide a third dimension to buildings, while all other features will be flat. Relative heights are denoted with the prefix ‘Rel’. These attributes are also applicable to the Tank, Glasshouse and Chimney Stack structures included in the data. The unit of measurement used for relative heights is metres. **RelHMax:** RelHMax (Relative Height Maximum) is the derived value from the calculation of AbsHMax (the calculated absolute value for the building height), minus AbsHMin (the calculated absolute value for ground height), i.e. RelHMax = AbsHMax – AbsHMin. **RelH2:** RelH2 (Relative Height 2) is the derived value from the calculation of AbsH2 (the calculated absolute value for the eave height), minus AbsHMin (the calculated absolute value for ground height). ### Use Cases The data can be used for modelling air pollution, siting solar panels, visualising planning applications in the context of surrounding buildings and also for urban density. Emergency services can also use it to know when and where to deploy specialist equipment. It can also be used to model heat loss, regulate requirements including high-rise gas safety, help with smart meter roll-out and analyse line of sight for small cell planning. It can help to manage overhead cable routing and assist in planning and maintaining water pressure to high-rise properties. Building Heights have been used for planning applications to show how a new office building would fit into existing buildings. Existing buildings were extruded and the 3D model for the new building was added to the map to show how it would look once constructed. Some fire and rescue organisations have created 3D models of buildings over a certain height in web mapping applications following the Grenfell Tower fire. It enables firefighters to see clearly whether there are any buildings over 18 meters in height before arriving at a incident and therefore what equipment to take. ## Supporting Documents **Technical Specification** * The [technical specification](https://docs.os.uk/os-downloads/products/maps-and-imagery-portfolio/os-mastermap-topography-layer/os-mastermap-topography-layer-technical-specification) provides detailed technical information about the product. It is targeted at technical users and software developers. **Supporting documents** * [OS MasterMap - Real-world object catalogue](https://www.ordnancesurvey.co.uk/documents/legends/os-mastermap-real-world-object-catalogue.pdf): This catalogue lists the real-world objects (RWOs) present in OS MasterMap data and the features and attributes associated with them. * [Getting started with styling guide](https://docs.os.uk/os-downloads/products/maps-and-imagery-portfolio/os-mastermap-topography-layer/os-mastermap-topography-layer-getting-started-with-styling-guide): This document provides information on how to style the OS MasterMap Topography Layer product. For related styling information, please refer to the Standard Styling Specification. * [Standard styling specification](https://docs.os.uk/os-downloads/products/maps-and-imagery-portfolio/os-mastermap-topography-layer/os-mastermap-topography-layer-standard-styling-specification): This document provides information on the Standard Styling Specification for the OS MasterMap Topography Layer product. * [Additional information on OS MasterMap Building Height Attribute.](https://beta.ordnancesurvey.co.uk/products/os-mastermap-building-height-attribute) * [OS products refresh dates](https://docs.os.uk/os-downloads/resources/product-refresh-dates). *** Links that may be useful: {% embed url="" %} {% embed url="" %} --- # 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/more-than-maps/data-demonstrators/topography-demonstrators/os-mastermap-r-demonstrators/os-mastermap-topography-layer.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.