OS MasterMap Topography Layer – November 2024 Release Note

This release note provides information about the November 2024 release of OS MasterMap (OSMM) Topography Layer.

OS MasterMap Topography Layer – September 2024 Release Note

This release note provides information about the September 2024 release of OS MasterMap (OSMM) Topography Layer.

OS MasterMap Topography Layer – August 2024 Release Note

This release note provides information about the August 2024 release of OS MasterMap (OSMM) Topography Layer.

OS MasterMap Topography Layer – June 2024 Release Note

This release note provides information about the June 2024 release of OS MasterMap (OSMM) Topography Layer.

OS MasterMap Topography Layer – May 2024 Release Note

This release note provides information about the May 2024 release of OS MasterMap (OSMM) Topography Layer.

OS MasterMap Topography Layer – April 2024 Release Note

This release note provides information about the April 2024 release of OS MasterMap (OSMM) Topography Layer.

OS MasterMap Topography Layer is the most detailed and accurate view of Great Britain's landscape. It includes features representing the manmade and natural environment, including: land cover, buildings, water, rail, height, heritage, structures, administrative boundaries, and roads, tracks and paths.

The OS MasterMap Topography layer is presented seamlessly with more than 500 Million real world objects – all uniquely identified – including roads, buildings, parks and waterways. All data is managed and maintained by Ordnance Survey within one of the world’s largest spatial databases.​

How to get this product

Access to this product is free for PSGA members. Find out if you are a PSGA member or try out a sample of OS MasterMap Topography Layer data by visiting the Topography layer product page here with links to all of the relevant resources. Alternatively, you can try out the full product by applying for a Data Exploration license here.

OSMM Topography Layer product count

The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.

Changed TOIDs

Numerous TOIDs (Topographic Identifiers) have changed since the last refresh, resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:

Discrepancies

In this release 7 errors were detected, of which, 2 have existed since the previous refresh. These are all considered to be minor errors and there are no major errors present.

We aim to have all errors resolved prior to the next release as part of ongoing quality improvements.

Next release

The next release of OS MasterMap Topography Layer is scheduled for 16 December 2024.

Land cover refinement changes

The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.

The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in December 2022. The single class land cover polygons will continue to feed through to product from April 2023.

The following two tables articulate this specification refinement:

Old land cover specification

New land cover specification

The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.

Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.

Annex A: Rural land cover specification refinement examples

Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.

Example one

Location of example one.

TOIDs for example one.

Source imagery of example area one for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Example two

Location of example two.

TOIDs for example two.

Source imagery of example area two for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Example three

Location of example three.

TOIDs for example three.

Source imagery of example area three for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

OSMM Topography Layer product count

The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.

Discrepancies

In this release 10 minor errors were detected, of which 2 have existed since the previous refresh. All errors are considered to be minor errors. We aim to have all errors resolved prior to the next release as part of ongoing quality improvement.

Land cover refinement changes

The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.

The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in

December 2022. The single class land cover polygons will continue to feed through to product from April 2023.

The following two tables articulate this specification refinement:

Old land cover specification

The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller, more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.

Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.

Changed TOIDs

Numerous TOIDs (Topographic Identifiers) have changed since the last refresh, resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:

Next release

The next release of OS MasterMap Topography Layer is scheduled for 24th June 2024.

Annex A: Rural land cover specification refinement examples

Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.

Example one

Location of example one.

TOIDs for example one.

Source imagery of example area one for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Example two

Location of example two.

TOIDs for example two.

Source imagery of example area two for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Example three

Location of example three.

TOIDs for example three.

Source imagery of example area three for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

OSMM Topography Layer product count

The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.

Discrepancies

9 minor errors were detected, which is 2 more than were found in the last refresh. Of these 9 errors, 2 have existed since the previous refresh. All errors are considered to be minor errors. We aim to have all errors resolved prior to the next release as part of ongoing quality improvement.

Land cover refinement changes

The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.

The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in December 2022. The single class land cover polygons will continue to feed through to product from April 2023.

The following two tables articulate this specification refinement:

Old land cover specification

New land cover specification

The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller, more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.

Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.

Changed TOIDs

Numerous TOIDs (Topographic Identifiers) have changed since the last refresh, resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:

Next release

The next release of OS MasterMap Topography Layer is scheduled for 13th May 2024.

Annex A: Rural land cover specification refinement examples

Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.

Example one

Location of example one.

TOIDs for example one.

Source imagery of example area one for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Example two

Location of example two.

TOIDs for example two.

Source imagery of example area two for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Example three

Location of example three.

TOIDs for example three.

Source imagery of example area three for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

The data model

OS MasterMap Topography Layer is grouped into feature themes. Within each theme there will be features deemed to belong to that theme. A feature can belong to more than one theme.

Each feature will have one or more versions of itself which can be tracked as a means of demonstrating change over time. New versions of features will replace existing features through COU, and features that no longer exist can be deleted as a result.

This page introduces the concepts of themes, features, and attributes applicable to OS MasterMap Topography Layer.

Themes

A theme is a set of features that have been grouped together for the convenience of users and to provide a high-level means of dividing the data on the layer 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.

A theme is created by applying rules based on the attributes of features. A theme rule can depend on the common values contained in the feature attributes. A feature is considered a member of each theme to which it passes a theme rule.

Themes are not part of the classification system of features for OS MasterMap. Because of this, a new theme can be created, for the convenience of our users, without in any way affecting either the existing themes or the classification of OS MasterMap features. An overview of each theme for OS MasterMap Topography Layer is given on the .

Features

In this Overview, the term 'real-world object' is used to describe a geographic entity that can be captured and represented in the data. A real-world object is represented by a feature in OS MasterMap data.

A complete list of the real-world objects and their feature representations is given in the OS MasterMap Real World Object Catalogue, which is available from the Related Links section at the bottom of the .

Each feature has one of three geometrical structures – a point, a line, or a polygon. A line feature will have a start and end node that reflects the start and end of the real-world object it represents. Where the start and end node are coincident, the feature created is structured as a polygon. Lines and polygons represent both the location and the geometry of the real-world object. Points do not necessarily represent the exact geometry of the real-world object, just the centroid of its location. Text features are used to provide additional information and context about real-world objects represented by point, line, or polygon features. They are represented as a point, which indicates the location where the text should be displayed.

Polygon features fit with each other topologically within structuring layers. This means that polygons sit adjacent to each other like pieces of a jigsaw puzzle, rather than on top of each other. In the image below, it can be seen that buildings (orange squared-off polygons), if ‘removed’, leaves their footprints in a land feature (green polygon); the land feature does not exist below the buildings.

Attributes

Each feature comes with an extensive set of attributes that provide information about the feature, for example, its identity, its relationship to other features, its geometry, and the kind of real-world object it purports to represent. Each type of feature has a different set of attributes.

There are two types of attribute information:

• Attributes that provide data about the real-world object the feature represents, such as its area or its nature.

• Attributes that provide additional information about the feature, such as its lifecycle and quality.

OS MasterMap Topography Layer provides attribution that can be searched for and queried within a GIS. Attribution makes it possible to select parcels of land with common features, for example, a polygon attributed as having coniferous tree cover.

OS MM Topography Layer product count

The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.

Changed TOIDs

Numerous TOIDs (Topographic Identifiers) have changed since the last refresh resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:

Discrepancies

In this release 23 errors were detected, of which, 2 have existed since the previous refresh. These are all considered to be minor errors and there are no major errors present.

We aim to have all errors resolved prior to the next release as part of ongoing quality improvements.

Next release

The next release of OS MasterMap Topography Layer is scheduled for 04 November 2024.

Land cover refinement changes

The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.

The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in December 2022. The single class land cover polygons will continue to feed through to product from April 2023.

The following two tables articulate this specification refinement:

Old land cover specification

New land cover specification

The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.

Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.

Annex A: Rural land cover specification refinement examples

Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.

Example one

Location of example one.

TOIDs for example one.

Source imagery of example area one for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Example two

Location of example two.

TOIDs for example two.

Source imagery of example area two for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Example three

Location of example three.

TOIDs for example three.

Source imagery of example area three for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

OS MasterMap Topography Layer was initially developed in response to the need for a national topographic dataset that offers users a more sophisticated type of data that represents the world in a more realistic way and is more aligned to the increasing use and functionality of geographic information systems (GIS) and spatial database technology within organisations.

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 regularly updated by ground and aerial survey to a regular schedule, and the data is captured and published to a consistently high standard.

Many users apply geographic products as a starting point to derive their own data, which can be time consuming and inefficient. This is particularly true where features in the data are amalgamations of more than one real-world feature, or even individual parts of a real-world feature. Where the feature represents a real-world feature that has an ‘area’, such as a building or a parcel of land, the feature is represented in the data as a polygon. This should provide opportunities for users to derive their data with greater efficiency and ease as features can be selected either singularly or in groups. The way, and, largely, the extent of a user’s ability to take advantage of the polygonised structure will depend on the systems in use in their organisation. However, most GIS have the necessary ‘data capture’ tools to analyse and interrogate the topography features.

OS MasterMap Topography Layer provides detailed attribution, through its descriptive terms, relating to the real-world object and the group of features it represents. This means certain types of analysis can be performed, without the user having to manually add their own attribution to the data. The themed attribution (see for more information) also means the user can apply their own criteria to refine the data into groups of features that meet their own specific requirements. An example of this would be finding buildings of a certain size by using the calculated area provided as one of the attributes.

It is important for many applications of geographic information (GI) to be able to identify where changes have taken place and the history of a feature's changes. This is important because users may need to learn how the landscape has altered and reflect those changes in their own data. Ordnance Survey updates

OS MasterMap Topography Layer on a regular basis, and these changes are passed on to users through a dataset called change-only update (COU). COU supplies just the features that have changed since the last update or customer user order. This should normally result in much less data needing to be processed and uploaded to the user’s holdings upon the arrival of each update. This is, however, dependent on how frequently the COU data is applied. Furthermore, OS MasterMap Topography Layer is the first product from Ordnance Survey to introduce the concept of feature lifecycles and unique referencing. This makes it possible to relate change in the real world to features in the digital environment, and to identify and manage that change to OS MasterMap Topography Layer so that users can, if they wish, keep their own data holdings up to date. This will also enable the user to assess the consequences of feature changes. It may even be possible, depending on the systems used, for users to roll back their holdings of OS MasterMap Topography Layer to a specific point in time. However, Ordnance Survey does not supply previous versions of any feature or dataset.

Thematic maps

One of the most common uses for GI is to produce maps that are coloured to highlight a particular value or property that a real-world feature may have; these are often called thematic maps. An example is given in the image below. This image was created by grouping the calculated area value attribute of each unit on an industrial park into one of five categories. Each category is ‘themed’ with its own colour. The ranges and colours are shown in the legend. Most computer systems offer the ability for features to be assigned a colour or style based on the value of an attribute; OS MasterMap Topography Layer has both the structure and attribution to make it relatively quick to produce such thematic maps. The result is data that is easier to customise, easier to interpret and more eye-catching.

Linking datasets

One common barrier to users is linking datasets together and sharing this data with other Ordnance Survey users, making greater use of their own data. To be able to link or ‘associate’ datasets together normally requires each dataset to have a common reference – one piece of information that is in all datasets. OS MasterMap Topography Layer can help to create links between users’ own datasets and

OS MasterMap features by using the TOID as a common reference. In this way, OS MasterMap Topography Layer provides a foundation dataset for a Digital National Framework that aims to help users of spatial data to derive more value by associating datasets together. Using a common reference can also provide such benefits to an organisation as removing ambiguity over a feature’s identity and allowing the faster retrieval of data when querying or analysing the data.

The Geography Markup Language (GML) and GeoPackage formats use the British National Grid (BNG) spatial reference system. BNG uses the OSGB36 (EPSG 27700) geodetic datum and a single Transverse Mercator projection for the whole of Great Britain. Positions on this projection are described using easting and northing coordinates in units of metres.

Vector tiles format is supplied in Web Mercator projection (EPSG:3857). Web Mercator projection uses WGS84 geodetic datum to render the vector tiles.

The More than Maps platform has an in-depth guide to coordinate reference systems and mapping using the British National Grid here.

System requirements

OS MasterMap Topography Layer data is designed for use as a digital map within GIS and database systems.

For details of Ordnance Survey’s Licensed Partners who can incorporate OS MasterMap Topography Layer in their systems, please see the Our Partners page on the OS website.

Ordnance Survey does not recommend either suppliers or software products. The most appropriate system will depend on many factors, such as the amount of data being taken, resources available within the organisation, the existing and planned information technology infrastructure or, last but by no means least, the applications in which OS MasterMap Topography Layer is to be used.

However, as a minimum, the following elements will be required in any system:

• A means of reading the data in its native format, or translating the data into a file format, or storing the data in a database.

• A means of storing and distributing the data, perhaps in a database or through a web-based service.

• A way of visualising and querying the data, typically a GIS.

There is more information on handling OS MasterMap Topography Layer in product supply.

Available formats for the product

• GeoPackage

• Vector tiles (MBTiles)

• Geography Markup Language (GML) 2.1.2

Coverage

Coverage is Great Britain (GB).

File size

File sizes vary greatly depending on tile size and the quantity of features present in a tile:

• GeoPackage 25km² tile range: Varies (dependent on AOI selection)

• Vector tile GB Supply: Approx. 20GB

• GML 25km² tile range: Varies (dependent on AOI selection)

• GML GB Supply: Approx. 47GB

Product update schedule

OS MasterMap Topography Layer is updated every 6 weeks. Information about the current product version, and information about future and past releases, can be found on the OS MasterMap refresh dates page of the OS website.

OS MasterMap Topography Layer is used extensively by businesses and organisations that need to relate their activities and / or their assets to the physical environment.

One of the most common uses for the product is by organisations who have their own GI and wish to examine it in relation to the real world around them. An example would be utility companies that have assets both at surface level and below surface level. They frequently need to visit these assets, either for repair, maintenance, or to add new assets. By viewing their infrastructure against the features in

OS MasterMap Topography Layer, it will help their crews locate the assets and become familiar with the area before they leave their depot, and it will allow them to provide a better user service by identifying those nearby premises that need to be notified about the works.

Taking this a stage further, many organisations need to derive their own GI from OS MasterMap Topography Layer. They use the individual features that Ordnance Survey provide to form the building blocks for their own sets of GI. Many local- and central-government organisations use the data in this way. A local authority, for example, may use it to maintain a register of land and buildings in their ownership.

Once they have the physical feature or group of features they are interested in, 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.

As more GI is created, it is possible to analyse the spread and distribution of features or activities and learn from their relationship to other physical features. For example, a police force might plot the locations of certain types of street crimes, and by analysing the pattern and the timing of the incidents against the local topography, they may be able to target their resources more efficiently.

OS MasterMap Topography Layer can also be used as part of a data modelling or a predictive modelling tool. 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 from a settlement or main road and cross referencing the information contained within OS AddressBase to identify an ideal catchment area. 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 also be used to model the sequence of events in any given type of emergency, so that their own resources and command centres are unlikely to be cut off or taken out of action by the emergency itself.

It is possible to customise OS MasterMap Topography Layer styling as a way of clearly communicating GI in reports and presentations. GI can be conveyed more meaningfully in a map than by text or tables, making it easier to get points across to many different types of audience, whether they are key decision-makers, people inside the organisation, or members of the public. OS maintains an OS MasterMap Topography Layer Stylesheets page on GitHub with predesigned, schema-specific styling guides for the product.

It should be noted that the ability of an organisation to develop any or all the applications mentioned above will depend, in part, on the systems they use. Most GIS are capable of performing, to a greater or lesser degree, the applications already mentioned. Examples of other product applications for OS MasterMap Topography Layer include the following:

• Land management and property development

• Site planning

• Citizen services

• Location-based services on mobile devices

• Environmental monitoring

• Tourism and promotional material

• Risk assessment

• User service centres

This section gives an overview of the nine themes of OS MasterMap Topography Layer:

• Administrative Boundaries

• Buildings

• Heritage and Antiquities

• Land

• Rail

• Roads, Tracks, and Paths

• Structures

• Terrain and Height

• Water

The main features of each theme are described in the following sub-sections. More detailed information about the nine themes, including the rules that govern which theme or themes are assigned to a feature, can be found in the product's Technical Specification.

Wherever possible, real-world objects are represented in their true surveyed position. However, for the sake of clarity of display or plotting, real-world objects may be generalised (for example, small juts in house fronts may not be shown). The normal methods of generalisation that can be applied to features are:

• Emphasis

• Selection for inclusion

• Simplification

• Omission

Real-world objects may also be simplified in the OS MasterMap Topography Layer, for example, a small group of trees may be recorded as a single point or polygon feature. The following sub-sections give a breakdown, by feature type, of the nine themes in greater detail, including regional and cultural special designations.

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 mereing and boundary descriptions, where needed for clarification, are also supplied.

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. With a few exceptions (for example, by describing government offices or hypermarkets), no distinction is currently made between residential, private, public, commercial, or industrial buildings.

Heritage and Antiquities

For Ordnance Survey purposes, antiquities are defined as existing artificial features of a date not later than AD 1714 (the date of the accession of George I). These antiquities are captured along with very important battlefield sites and natural features connected with important historic events. Features and sites of a date later than AD 1714 may be treated as antiquities as an exception if they are of national importance.

The investigation, recording and surveying of archaeology is the responsibility of English Heritage, Historical Environment Scotland (HES) and Cadw (Wales). Antiquity find sites are not shown in OS MasterMap Topography Layer. Ordnance Survey has no responsibility for defining the authenticity of distinctive or descriptive names of antiquities.

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.

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, for example, from railway station to railway station, or from an industrial building to a private quarry.

Roads, Tracks, and Paths

Roads

For Ordnance Survey purposes, 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.

Tracks

A track, for Ordnance Survey purposes, 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’. All tracks are described as ‘Track’, or ‘Tk’ if required to be abbreviated. Distinctively named tracks have their name recorded, for example, HICKS LANE (Track).

Paths

For Ordnance Survey purposes, a path is defined as any established way other than a road or track. They can be considered as either ‘made’ or ‘unmade’.

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.

Terrain and Height

These are features that 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.

Water

Water features are defined as features that contain, delimit, or relate to real-world objects containing water.

This section introduces two aspects of deriving additional value from OS MasterMap Topography Layer:

• The first aspect is utilising the referencing and change-tracking attributes to identify and manage the impact of change on a user’s data. It discusses the process of applying change and the implications for archiving data.

• The second aspect is associating user data and OS MasterMap Topography Layer using the TOID as a common reference. This creates the potential to share data between departments and organisations. It explains what data association is and it gives examples of how data association can bring benefits to organisations.

Change management

The feature-reference and change-tracking attributes provide the opportunity for users to put in place a change-management regime. The system that the user uses to translate and load OS MasterMap Topography Layer should use the TOID and version information to update their local holding when a COU is taken onboard.

The software used to manage the holding needs to handle three types of situation: features that have been deleted (known as Deletes), features that are new (known as Inserts), and features that have changed (known as Updates). The software should resolve Deletes as a priority. It is important that COUs are processed with Deletes first, then Inserts and Updates. This is to ensure that updates are applied in the correct order.

Deletes

• In the COU, there is a list of features that have been deleted since the last time the user took data. There are some additional considerations with deleted features, but in essence, the software should find all the TOIDs and versions on the deleted features list in the COU, locate them in the main holding, and remove those features.

• In the case of superseded and deleted features, these could be removed totally from the user’s holding, but it may better suit the requirements of the user to archive them for future reference.

Inserts

• With a new feature, called an Insert, the software compares each TOID in the COU against the TOIDs in the existing holding. If the TOID exists in the COU but not in the main holding, it is considered an Insert and the software should put it into the holding.

Updates

• If the TOID already exists in the holding, the software needs to compare the version number in the existing holding against the version number in the COU. If the version number in the COU is higher than in the existing holding, the software needs to take out the existing version of the feature and replace it with the version contained in the COU. If, on the other hand, the COU version number is lower than the COU version number, the feature should be ignored.

Archiving the OS MasterMap data holding

As OS MasterMap features progress through their lifecycles, it is possible to develop snapshots of the features by holding superseded versions in a local data archive. By holding and maintaining a local data archive, users will be able to interrogate previous views of the world straight from their local data holding.

It is important to consider carefully how to archive OS MasterMap Topography Layer features, and what requirements the applications and users will have to access the older information. Archiving may be done by simply writing older versions of the data to hard media, or by a more sophisticated system of keeping historical data live. It is important for users to recognise their own unique requirements (be they user, statutory or regulatory requirements) as archiving can become a significant overhead in terms of storage.

Before designing or implementing an archive of OS MasterMap Topography Layer, it is advisable for a user to discuss requirements with their system supplier.

Obtaining OS MasterMap Topography Layer data

This getting started guide shows you how to load OS MasterMap Topography Layer into several commonly used geographical information system (GIS) applications.

Product formats

OS MasterMap Topography Layer is available the following formats:

• GeoPackage (area of interest – AOI – only)

• Vector tiles (MBTiles)

• Geography Markup Language (GML) 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 5km2 tiles, but features are not clipped at the tile edges, resulting in what is called “hairy” tiles. All tiles contain six elements:

• Cartographic Symbol

• Cartographic Text

• Boundary Line

• Topographic Point

• Topographic Line

• Topographic Area

Media

OS MasterMap Topygraphy Layer is not available via hard media supply.

Using GeoPackage and vector tile formats

This getting started guide focuses on using the product in GML and shapefile format.

For guidance on using the product in GeoPackage or vector tiles formats, please see the following generic getting started guides:

This guide contains instrictions for the following GIS applications:

OS MasterMap Topography Layer contains features that represent objects in the physical environment, such as buildings, fields, fences, and letter boxes. It also includes intangible objects, such as county boundaries and the lines of mean high or low waters. There are over 500 million features in the product. Coverage includes the whole of Great Britain (i.e. England, Scotland, and Wales).

Product highlights

The key characteristics and benefits of OS MasterMap Topography Layer are:

• Individual real-world topographic features are represented by points, lines, and polygons, each with their own unique reference, called a topographic identifier (TOID).

• 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.

• It 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 and with coordinates delivered in British National Grid (with the exception of vector tiles format, which is supplied in Web Mercator projection – EPSG:3857).

• The data is developed, managed and maintained by Ordnance Survey within one of the world’s largest spatial databases.

• The data is delivered as a seamless, geographically contiguous area for the whole of Great Britain.

These characteristics mean that a user may use the product in a wide variety of ways, including:

• Improving the accuracy of their own derived data.

• Improving their data capture processes.

• Creating consistency and achieving maintainable standards within geographic data holdings.

• Establishing a common reference between their own datasets and data they may wish to share with other organisations.

• Improving the visual clarity of data and aiding the visual interpretation of data.

• Using OS products in an integrated manner to derive additional information. For example, appending OS AddressBase data to OS MasterMap Topography Layer buildings data to derive building names and addresses.

• Identifying and managing change in their area of interest (AOI).

• Creating historical views of their AOI.

• Enhancing the queries that can be run on their data, thereby providing better information for decision making.

Index

This overview document provides a high-level introduction to OS MasterMap Topography layer and covers the following topics:

• Product Purpose

• Product applications

• Product details

• Styling

• Product themes

• Coordinate reference systems

• Product supply

• Change management and data association

Stylesheets are available for OS MasterMap Topography Layer to optimise the cartographic representation of the product, assisting users in visualising and identifying topographic features at a glance. Users can choose the style that suits their use case best from the four different styles available: backdrop, light, outdoor, and standard.

The predefined stylesheets are available in four formats (QML, LYR, 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.

OSMM Topography Layer product count

The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.

Changed TOIDs

Numerous TOIDs (Topographic Identifiers) have changed since the last refresh, resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:

Discrepancies

In this release 5 minor errors were detected, of which 2 have existed since the previous refresh. All errors detected are considered to be minor. We aim to have all 5 errors resolved prior to the next release as part of ongoing quality improvements.

Next release

The next release of OS MasterMap Topography Layer is scheduled for 12 August 2024.

Land cover refinement changes

The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.

The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in December 2022. The single class land cover polygons will continue to feed through to product from April 2023.

The following two tables articulate this specification refinement:

Old land cover specification

New land cover specification

The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller, more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.

Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.

Annex A: Rural land cover specification refinement examples

Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.

Example one

Location of example one.

TOIDs for example one.

Source imagery of example area one for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Example two

Location of example two.

TOIDs for example two.

Source imagery of example area two for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Example three

Location of example three.

TOIDs for example three.

Source imagery of example area three for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

These instructions are based on QGIS version 3.22.4 and assume you have set the default coordinate reference system to British National Grid (EPSG 27700).

Loading and displaying the GML supply

There are two ways to load the GML supply into QGIS: You can use drag and drop or the Data Source Manager.

Using drag and drop

To load the GML supply using drag and drop:

1. Open an existing QGIS project or create a new one.

2. In the file system on your computer system (for example, in Windows Explorer), select the GML data (.gz file).

3. Drag and drop the file directly into the QGIS UI.

4. In the Select Items to Add dialog:

If you use multiple screens, this dialog may open on another screen.

• Select each required layer or click Select All to select all layers.

• Check the Add layers to a group option.

This groups the layers by OSMM Topography Layer tile reference.

• Click Add Layers.

The GML data will now display in both the Layers panel and the map area.

Using Data Source Manager

To load the GML supply into QGIS using Data Source Manager:

1. Open an existing project or create a new one.

2. In the Layer menu, click Data Source Manager.
3. In the Data Source Manager dialog:

   • Select Vector from the data menu on the left.

   • In Source > Vector Dataset(s), click ‘…’, navigate to and select the GML on your computer.

   • Click Add.

1. In the Select Items to Add dialog:

If you use multiple screens, this dialog may open on another screen.

• Select each required layer or click Select All to select all layers.

• Check the Add layers to a group option.

This groups the layers by OSMM Topography Layer tile reference.

• Click Add Layers.

The data will now display in both the Layers panel and the map area.

Layer order and rendering

Data is typically grouped by tile reference in the Layers panel. If you open two or more OSMM Topography Layer layers simultaneously (for example, TopographicArea and BoundaryLine), you may need to reorder the layers to see the data correctly.

You can reorder layers using drag and drop. We recommend the following layer order: CartographicText, CartographicSymbol, TopographicPoint, BoundaryLine, TopographicLine and TopographicArea.

GML data limitations

Using GML data in QGIS is not always the best option. You should consider converting your data to another format (for example, shapefile) for the following reasons:

• When working with multiple tiles of 5km2 OSMM Topography Layer data, GML data does not always merge seamlessly.

• Rendering performance of GML data in QGIS is not as good as other formats, because GML data cannot be spatially indexed.

The sections that follow show you how to convert GML data to shapefile and how to apply a spatial index to shapefiles.

Converting GML to shapefile

To convert GML to shapefile in QGIS:

1. In the Layers panel, right-click on the layer you want to convert and click Export > Save Features As....

1. In the Save Vector Layer as… dialog:

   • Format: Select ESRI Shapefile.

   • File name: Click …, navigate to the folder in which you want to store the shapefile, name the file, and click Save.

   • Check the Add saved file to map option.

   • Click OK.

You can watch the export progress in the blue progress bar at the bottom of the QGIS UI. When the process is complete, the shapefile layers will display in the Layers panel and the map area.

1. Repeat steps 1 - 2 above for each layer (for example, TopographicLine, CartographicText…) that you want to convert.

Applying a spatial index to shapefiles

When working with shapefiles, we recommend you apply a spatial index to the data, particularly when loading large or national sets of data. This significantly improves performance when rendering and panning the data.

To apply a spatial index to a shapefile in QGIS:

1. In the Layers panel, right-click on the shapefile layer you want to index and click Properties in the context menu.

1. In the Layer Properties dialog:

   • Select Source in the navigation menu on the left.

   • In Geometry click Create Spatial Index.

   • Click OK to close the confirmation dialog.

   • Click Apply and then OK.

Your shapefile layer will now be spatially indexed; this improves rendering and querying performance.

1. Repeat steps 1 and 2 above for each layer you want to create an index for (for example, TopographicLine, CartographicText…).

There are several options available to customers when ordering data in GML format that provide additional metadata or aid data management.

Chunk files

To make the management of large areas easier, data is split into chunks, each of which covers a nominal square area. Data can also be supplied as part of a squared area to complete a predefined area as part of a nominated file size. Two types of chunks are available: geographic and non-geographic chunks. Chunk boundaries are imposed purely for the purpose of dividing large supply areas into pieces of manageable size in a geographically meaningful way. Both Full Supply and updates (whether COU or Full Resupply) are chunked.

Geographic chunking option

As OS MasterMap Topography Layer data is seamless, GML files containing large areas could be very data intensive. In order to provide files of a manageable size, data supplies are divided into chunks of user-specified size, each of which is supplied in a separate GML file. The figure below illustrates how geographic chunks work:

The process of chunking has the following steps:

1. The user submits an AOI by either drawing an AOI or uploading a pre-defined AOI to the OS Data Hub platform (or OS Orders).

2. Both online ordering systems create a grid covering the entire area based on the user-specified size (for example, 25km²).

3. Each square within the grid forms a chunk file.

4. Each feature that intersects that square goes into the chunk file.

In the case shown in the image above, 10 chunks have been created. The central chunk is a complete grid square; the other chunks are partly bounded by the data selection polygon. The upper-left square shows the effect when the data selection polygon crosses a grid square twice – i.e. two or more separate chunks are created.

A consequence of chunking is that some features are supplied in more than one chunk. Systems reading OS MasterMap Topography Layer data must identify and provide the option to remove these duplicated features.

If a chunk contains no information relating to a user’s selected themes, then it is not supplied.

Chunks cannot be treated as persistent data management units; as it is a floating grid, the origin of the chunking grid may differ between orders, particularly if the contract area changes or if a different chunk size is ordered.

Supply of OS MasterMap Topography Layer features in chunk files

The packaging of a seamless dataset into chunks means that where a feature lies across or touches the boundary of several chunks, it is supplied in all the related chunks. This is because an individual feature is the smallest unit within the OS MasterMap Topography Layer, and it cannot be physically split into two or more parts.

When a polygon falls across a chunk edge, but its bounding line(s) lie outside, it may not be included in that chunk. It will be included in the adjacent chunk, unless the polygon is at the edge of the contract area, in which case, the line will not be supplied at all.

When a polygon changes so that it no longer falls in the same chunk, for instance, when an OS MasterMap Topography Layer feature used to lie partly inside a chunk and instead is now reduced in size so it is wholly within an adjacent chunk, it is reported as a deleted feature (a Delete) in one chunk and as a modified feature (new version, known as an Update) in the adjacent chunk. This is shown in the diagram below.

It is possible for OS MasterMap Topography Layer features with point geometry to be included in multiple adjacent chunk files. This is because the query used to populate a chunk file includes all features that touch its boundary, and this boundary is shared with adjacent chunks. Therefore, loading software must be able to identify and remove duplicate point features across multiple files in the same way as features represented by lines and polygon geometries.

Non-geographic chunking option

This supply format delivers the files in a fixed nominal size, as opposed to a given geographic area depending on user preference.

Unlike in geographic chunking, each feature in non-geographic chunking appears in only one chunk file. It is possible for features from various geographic locations to appear in a single file, and for adjacent features to appear in different files. Non-geographic chunk files are designed for use as a set to load spatial databases but can be used in a file format if all chunks are translated or imported into the system at the same time.

It is not possible to tell in which file a particular feature will be found before reading the files. With non-geographic chunks, there are no duplicate features lying across chunk edges; this speeds up the translation process.

The features shown in red below can end up in the same non-geographic chunk even though they are not adjacent to each other.

Feature Validation Dataset

The Feature Validation Dataset (FVDS) is a set of files that can optionally be supplied with either a Full Supply COU or an AOI COU of an OS MasterMap Topography Layer order in GML format. The FVDS allows a user to validate that the data holding 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 is not necessary for users to order it with every supply, as processing it will slow the translating process. 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 itself divided into files on a non-geographic basis, using a 10MB nominal file size.

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. Each .csv file is compressed to a .gz file using the same compression algorithm used for OS MasterMap Topography Layer GML files.

GML summary file

An order summary file in GML format will be supplied with all OS MasterMap Topography Layer orders, containing the order information specified by the user. This information includes:

• The order number

• Query extent polygon(s) of the order

• The order type: Full Supply or COU (for COU orders, the change since date will be included)

• The themes requested

• The chunk type: Non-geographic or geographic

• The chunk size (in MB for non-geographic chunks; in km² for geographic chunks)

OS MasterMap Topography Layer incorporates a web-based ordering system that allows users to order their initial data supply and any updates, obtain price estimates and view details of their holdings on demand. The product is supplied as an online download. You can download data in its various formats from the .

Please note that some formats are only available via , Ordnance Survey's legacy ordering system; these formats are indicated in the following table:

* Feature Validation Dataset (FVDS) and Change-Only Update (COU) available.

† Only available via OS Orders.

There are two main supply options available for OS MasterMap Topography Layer: Full Supply or COU.

Initial Supply refers to the first order of OS MasterMap Topography Layer that a user makes, which will contain all features for all the layers selected for the area covered by the order. Upon Initial Supply, users can select whether they would like to receive future data updates as COU (user receives only the tiles/features that have changed since the last update) or a Full Supply (user receives all tiles/features regardless of whether they have changed since the last product update). COU data contains new and updated versions of features (known as Inserts and Updates, respectively), and information about departed features (known as Deletes); any feature within the area covered by the order that has not undergone any change will not be supplied.

The advantage of taking a COU Supply rather than a Full Supply is that, if applied regularly, the amount of data that must be processed and loaded is much smaller with a COU Supply. Users may request updates of the latest changes in their AOI, at any time, using the online service. Updates can either be for specified AOIs or GB wide.

OSMM Topography Layer product count

The following table contains product counts for this release of OSMM Topography Layer data. The dates shown are extraction dates, not release dates.

Changed TOIDs

Numerous TOIDs (Topographic Identifiers) have changed since the last refresh, resulting in a visual difference in the data. The list below shows a sample of changed TOIDs and their locations that you can use as 'lookup samples' to validate that your latest supply has updated correctly:

Discrepancies

In this release 23 errors were detected of which 2 have existed since the previous refresh. These are all considered to be minor errors and there are no major errors present.

We aim to have all errors resolved prior to the next release as part of ongoing quality improvements.

Next release

The next release of OS MasterMap Topography Layer is scheduled for 23rd September 2024.

Land cover refinement changes

The land cover specification for rural geographies has been refined. The Mountain and Moorland refinement was completed in 2022.

The rural geography updates began capture in May 2022. The initial updates fed through to the July 2022 release of OSMM Topography Layer, with the multi class land cover polygons completed in December 2022. The single class land cover polygons will continue to feed through to product from April 2023.

The following two tables articulate this specification refinement:

Old land cover specification

New land cover specification

The land cover specification refinement means that the rural land cover data within OSMM Topography Layer will become more granular, producing a more detailed view made up of smaller more numerous polygons. This provides users with more accurate data that meets each individual’s specific requirements. These changes are purely refinements and do not change the data attribution.

Annex A shows three examples of how the rural land cover refinement is being translated into OSMM Topography Layer.

Annex A: Rural land cover specification refinement examples

Below are three real-world examples of how the rural land cover specification refinement has affected the data within OSMM Topography Layer. The examples showcase three areas in southern Scotland where the specification refinement has broken up one land polygon within the Topographic Area Feature Type into smaller, separate polygons.

Example one

Location of example one.

TOIDs for example one.

Source imagery of example area one for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – July 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Example two

Location of example two.

TOIDs for example two.

Source imagery of example area two for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

Example three

Location of example three.

TOIDs for example three.

Source imagery of example area three for comparative purposes:

Data before the rural land cover specification refinement update (OSMM Topography Layer – August 2022):

Data after the rural land cover specification refinement update (OSMM Topography Layer – October 2022):

These instructions are based on Cadcorp SIS Desktop Express 9.0.2511 and assume you have set the default coordinate reference system to British National Grid (EPSG 27700). These instructions also work for the fully licenced version of Cadcorp SIS Desktop.

Loading and displaying the GML supply

There are two ways to load the GML supply into Cadcorp SIS Desktop: You can use drag and drop or add and overlay.

Using drag and drop

To load and display the GML supply using drag and drop:

1. Open an existing project or create a new one.

2. In the file system on your computer system (for example, in Windows Explorer), select the GML data (.gz file).

3. Drag and drop the file directly into the Map area in Cadcorp SIS Desktop.

Data processing will begin automatically. You can monitor the progress by watching the spinning blue circle in the bottom left of the UI.

When processing is complete, the data will display in the Maps panel and Map area.

Cadcorp produces their own OS MasterMap Topography styling, which automatically styles your OMMM Topography data. If you cannot see your data, zoom to > 1:4,000 scale and it should become visible.

Adding an overlay

To load and display the GML supply by adding an overlay:

1. Open an existing project or create a new one.

2. From the Home tab, click Add Overlay.
3. In the Overlay Types dialog:

   • Click Files in the left navigation menu.

   • Click File in the options on the right.

   • Click Next>.

1. In the File Browser dialog:

   1. Navigate to and select the GML data (.gz file) you want to load.

   2. Click Finish.

Data processing will begin automatically. You can monitor the progress by watching the spinning blue circle in the bottom left of the UI.

When processing is complete, the data will display in the Maps panel and Map area.

Cadcorp produces their own OS MasterMap Topography styling, which automatically styles your OMMM Topography data. If you cannot see your data, zoom to > 1:4,000 scale and it should become visible.

These instructions are based on ArcMap version 10.8.1. and assume you have set the default coordinate reference system to British National Grid (EPSG 27700).

Loading and displaying the GML supply using the Quick Import tool

You can import GML data into ArcMap using the Quick Import tool that converts the GML into file geodatabase (.gdb).

To load GML data into ArcMap:

1. Open ArcCatalog and click and (ArcToolbox icon) in top toolbar to open the ArcToolbox.

1. In ArcToolbox, expand Data Interoperability Tools and click Quick Import.

1. In the Quick Import dialog, click … (next to the Input Dataset field), and navigate to and select your OS MasterMap Topography GML data.

1. In the Specify Data Source dialog:

   • Format: GML SF-0 (Geography Markup Language Simple Features Level SF-0 Profile) will be detected automatically.

   • Coord. System: Enter British_National_Grid or click … and select it in the dialog.

   • Click OK.

1. In the Quick Import dialog:

   • Output Staging Geodatabase field: Click (file browser icon), navigate to and name the file geodatabase (.gdb) folder, and click Save.

   • Click OK to start the Quick Import.

When the import process is complete, a message will display in ArcCatalog. To display the GML data in ArcMap:

1. Open an existing project or create a new one.

1. In the Add Data dialog:

   • Select the layers you want to load. You can select multiple layers at the same time to save repeating these steps for each layer in the file geodatabase.

   • Click Add.

Your geodatabase layers will now display in both the Table of Contents panel and the map area.

Loading and displaying shapefiles

As an alternative to using ArcMap’s Quick Import tool (previous section), you can convert your GML data to shapefile using FME and QGIS, and then add the shapefiles directly to ArcMap.

To load shapefiles into ArcMap

1. Open an existing project or create a new one.

1. In the Add Data dialog:

   • Navigate to the shapefiles you want to load. If the relevant folder does not display, click (Connect to Folder icon) and navigate to the file geodatabase folder from there.

   • Select the shapefiles that you want to load. You can select multiple layers at the same time to save repeating these steps for each shapefile.

   • Click Add.

Your shapefiles will now appear in both the Table of Contents panel and the map area.

You may need to reorder the layers to see the data correctly. You can reorder layers using drag and drop. We recommend the following layer order: CartographicText, CartographicSymbol, TopographicPoint, BoundaryLine, TopographicLine and TopographicArea.

The following instructions are based on ArcGIS Pro version 2.8.1 and assume that you have access to and knowledge of the UK Data Loader and the Data Interoperability Extension to convert the supplied GML into a suitable ArcGIS Pro format.

Loading and displaying the GML supply using UK Data Loader

The UK Data Loader is an ArcGIS toolbox. It contains a set of tools that primarily allow loading of Ordnance Survey data into an ArcGIS workspace.

If the UK Data Loader is not already installed, we recommend you add the folder containing the toolbox into your documents. More information on installing the UK Data Loader is available in ESRI’s . This guide also provides instructions for processing Change Only Updates (COU) for OSMM Topography Layer.

Using the UK Data Loader involves two steps: Converting the GML supply and loading the converted file geodatabase into ArcGIS Pro.

Converting the GML supply to file geodatabase

To load the GML data into ArcGIS Pro using the UK Data Loader:

1. Open an existing project or create a new one.

You may want to select a basemap for backdrop context.

1. From the View tab, select Catalog View.

1. In the Catalog view, navigate to the location in which your UK Data Loader toolbox is saved.

You may need to connect to the relevant folder using the Add Folder option in the Insert tab.

1. Open the toolbox, navigate to OS MasterMap Topography Layer > Load OSMM Topography Data, right- click on the script, and click Open in the context menu.

1. This will open the Geoprocessing panel in which you can set the parameters for running the script:

   • Source Data Folder: Navigate to and select the GML file(s) required.

   • Existing Destination Workspace: Navigate to and select the pre-existing file geodatabase (.gdb) folder to load the data into.

   • Logging File Folder: Navigate to and select a folder into which to save the log that will be created during data processing. This is important because any error messages will be captured here. These may help identify issues.

   • Feature Class / Table Prefix: Enter a prefix for your tables (for example, Topo_).

   • Create Annotation Line Features: Check this option if it is available and required. This checkbox option is only available in older versions of ArcGIS Pro/UK Data Loader.

This may take some time, depending on the number of 5km OSMM Topography Layer tiles being processed.

On completion, the OSMM Topography Layer data will be saved to the destination file geodatabase, which can then be loaded into the workspace by following the instructions in the next section.

Loading and displaying data from the file geodatabase

Having converted your GML data to file geodatabase using the UK Data Loader (or other tools listed in this guide), you can now load the OSMM Topography Layer GDB into your ArcGIS Pro workspace.

To load and display the file geodatabase in an ArcGIS Pro workspace:

1. Open an existing project or create a new one.

You may want to select a basemap for backdrop context.

1. From the Map tab, select Add Data.

1. In the Add Data dialog, navigate to and select the file geodatabase (.gdb) containing the OSMM Topography Layer data, and then click OK.

1. In the selected file geodatabase (.gdb) select the feature classes that you want to load and then click OK.

You can select multiple feature classes at once to save repeating these steps for all the OSMM Topographic Layer features.

Your OSMM Topography Layer feature classes will now appear in both the Contents panel and map area.

You may need to reorder the layers to see the data correctly. You can reorder layers using drag and drop. We recommend the following layer order: CartographicText, CartographicSymbol, TopographicPoint, BoundaryLine, TopographicLine and TopographicArea.

Loading and displaying shapefiles

As an alternative to using the UK Data Loader, you can load OSMM Topography Layer shapefiles directly into your ArcGIS Pro workspace. You need to first convert your GML data to shapefile.

Translation tools available in FME and QGIS to convert the GML data to shapefiles.

To load and display shapefiles in an ArcGIS Pro workspace:

1. Open an existing project or create a new one.

You may want to select a basemap for backdrop context.

1. From the Map tab, select Add Data.

1. In the Add Data window, navigate to and select the shapefiles (.shp) containing the OSMM Topography Layer data, and then click OK.

You can select multiple shapefiles at once to save repeating these steps for all the OSMM Topographic Layer features.

Your OSMM Topography Layer shapefiles will now display in both the Contents panel and map area.

You may need to reorder the layers to see the data correctly. You can reorder layers using drag and drop. We recommend the following layer order: CartographicText, CartographicSymbol, TopographicPoint, BoundaryLine, TopographicLine and TopographicArea.

These instructions are based on FME Desktop 2022.1.1.

Loading and displaying the GML supply

To load and display the GML supply in FME Desktop 2022.1.1.

1. Open an existing workspace or create a new one.

2. From the Reader tab click Add Reader…

1. In the Add Reader dialog:

   • Format: Select OGC GML (Geography Markup Language).

   • Dataset: Click …, and navigate to and select the GML file (.gz) in the file browser.

   • Coord. System: Select ESPG: 27700 (British National Grid).

   • Click OK.
2. In the Select Feature Types dialog select the required layers and click OK.

This dialog may take a while to load. You can watch the progress in the green bar at the bottom left of the FME window.

Figure 53:FME Desktop Select Feature Types dialog

When processing is complete, your features will appear as readers in the FME workspace.

1. Right-click one of the feature readers and click Connect Inspector in the context menu.

The Inspector will automatically connect to the reader.

The Inspector will automatically connect to the reader.

1. Click the Inspector and then click the Run to this icon (green triangle above the inspector).

2. In the Translation Parameter Values dialog click Run.

You can watch the loading progress in the Translation Log below the main workspace.

When the run command has completed, the GML table and features will display in the Visual Preview area below the main workspace.

1. Repeat steps 5 to 7 above for each layer (feature type) you want to view.

Converting GML to shapefile

You can use FME to convert GML data to other geospatial and non-spatial formats. The instructions below demonstrate how to convert GML data to shapefile, but you can adapt them for different formats.

To convert GML to shapefile in FME Desktop:

1. Repeat Steps 1 to 4 of the previous section (Loading and displaying the GML supply).

2. From the Writers tab click Add Writer…

1. In the Add Writer dialog:

   • Format: Select ESRI Shapefile.

   • Dataset: Click …, and navigate to and select the folder in which to save your translated data.

   • Coord. System: Select ESPG: 27700 (British National Grid).

   • Click OK.

1. In the Select Feature Type dialog select the layers you want to convert and click OK.

This dialog may take a while to load. You can watch the progress in the green bar at the bottom left of the FME UI.

1. Connect each reader to its matching writer by dragging the grey triangle on the reader to the red triangle on the writer.

1. In the main toolbar click (Run icon) to start the translation.

1. In the Translation Parameter Values dialog, check that the source and destination file locations are correct and click Run.

You can watch the conversion progress in the Translation Log below the main work area. When the conversion is complete (indicated by a message similar to the one below), both the GML files and Shapefiles will be available in your chosen folders and in the navigator.

These instructions are based on MapInfo Professional 2019 and assume you have set the default coordinate reference system to British National Grid (EPSG 27700).

The sections below provide instructions for both working with GML data and converting to MapInfo TAB.

Loading and displaying the GML supply

To load and display the GML supply directly in MapInfo Professional:

1. Open an existing workspace or create a new one.

2. From the Home tab, click Open > Universal Data.

1. In the Specify Data Source dialog:

   • Format: Select GML (Geography Markup Language).

   • Dataset: Click …, and navigate to and select the GML file (.gz) in the file browser.

   • Click OK.

1. In the Select Layers dialog, select the layers you want to load and click OK.

Your GML data will now display in the Maps panel and map area.

Converting GML to MapInfo TAB

To convert the GML supply to MapInfo TAB in MapInfo Professional:

1. Open an existing workspace or create a new one.

2. In the Home tab, click Open > Universal Data.
3. In FME Quick Translator, click Translate.
4. In the Set Translation Parameter dialog:

   • Reader Format: Select GML (Geography Markup Language).

   • Reader Dataset: Click …, and navigate to and select the GML file in the file browser.

   • Format: Select MapInfo TAB (MAPINFO).

   • Dataset: Click …, and navigate to and select the folder you want the translated data saved to.

   • Click OK.

You can watch the translation progress log in the FME Quick Translator. It will take some time; a single 5km tile of OSMM Topography Layer in GML format takes approximately 30 seconds. When the process is complete, a message similar to the example below will display.