OS NGD Transport Network
A Lightning Talk
Last updated
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OS Data HubA Lightning Talk
Last updated
There are 17 geometry layers and 8 cross reference layers in the OS NGD Transport Network Collection. All of them share geometry with OS MasterMap Highways Network, however where Highways only referenced features, in OS NGD they have been given a geometry - Road, Street, Path and junction.
The extra attribution on Road Links to include information about Pavements has created Schema Version 2 for Road Links
The data in OS NGD Transport Network is very similar to that of OS MasterMap Highways Network however, there are two major differences:
Features comprising several links or nodes that in OS MasterMap Highways Network are only referenced are given an explicit geometry in OS NGD data. These include the Road, Street, Path and Road Junction that make up these features
In OS MasterMap Highways Network the references between Road, Street or Path and the Road or Path Link were arrays. Due to the new OS NGD data formats of GPKG and CSV there is no longer an array data type and these are held as a row per reference
The data structure of the Roads part of the Transport Network:
Road Link. Individual links between junctions with other roads or paths that are the basic building blocks of the road network. These reference the start and end road nodes and reference the RoadTrackPath polygon that they sit inside.
Road Nodes. Node points at the start or end of Road Links. These reference and are referenced by Road Links and also Road Junctions.
Connecting Node. Where a Road Link starts or ends at a junction with a path instead of a road the Road Link references a Road Node that has the same osid as the Connecting Node from the Paths data
Road. Merged geometry of the Road Links that make up a complete named road, such as the M5. The Road/Road Link Ref table gives the link between Roads and their constituent Road Links.
Street. merged geometry of the Links that make up a complete Street. This could be a named road, numbered road or path and will be identified with a USRN (Unique Street Reference Number). The Street/Road Link Ref table gives the link between Streets and their constituent Road Links
The data that forms the Paths part of the Transport Network. As of September 2023, this has been extended to full GB coverage as opposed to just urban areas:
Path Link. individual links between junction points that are the basic building blocks of the path network. These reference the start and end path nodes.
Path Nodes. Node points at the start and ends of Path Links. These reference, and are referenced by, Path Links.
Path. Merged geometry of the Path Links that make up a complete named path, such as the M5. The Path/Path Link Ref table gives the link between Paths and their constituent Path Links.
Connecting Link. A link from the node at the end of a path to the nearest Road Link. The Road Link geometry splits where Connecting Links meet the Road forming junctions between roads and paths.
Connecting Node. A node at the road end of a Connecting Link. These have the same osid as the Road Node at that junction on the road network. This means that for routing purposes Connecting Nodes are not required and the Road Nodes at the same location used instead.
The data that forms the Pavements part of the Transport Network:
Pavement Link. Pavement Links are created from the same geometry as Road Links but only the parts where pavement is present in the underlying topographic data. This means that as the entire Road Link is not present the Pavement Links do not form a network. The Pavement Links reference the underlying Road Link features. Where a pavement is present on both sides of the road there will be 2 links in the data with the same geometry, one for the left side, one for the right side. The attribution includes:
Presence of pavement to the left or right side of the road (relative to direction of digitising)
Minimum and average width of pavement width in m
Road Link. The Road Link data now contains attribution relating to the presence of pavements along the entire length of the Road Link. This includes:
Overall presence and presence to the left or right of the Road Link (relative to direction of digitising) as both length and percentage
Minimum and average width of pavement present
The data that forms the Railways part of the Transport Network:
Railway Links have been created from a 1:10,000 scale cartographic rail dataset and are a topologically structured link dataset. How many linear features to show for sets of mainline rails or sidings have been made by cartographers based on cartographic representation, not an algorithm. The Railway Links are broken up at junctions, where the track splits, at stations, or where attribution changes along the length of the line, such as if the railway changes from being on an embankment, to on a structure or from Passenger to Siding. The attribution includes:
Description – Main Line, Funicular, Mineral, Preserved, Tram, etc.
Gauge – Standard, Narrow, Broad, Monorail
Structure – In Cutting, On Bridge, In Tunnel, On Embankment, etc.,
Use – Freight, Passenger, Mineral, etc.
How many tracks – Single, Multiple, Siding
Status – Active, Inactive
These appear at the start and end of Railway Links and can represent:
Junction, Station, Terminal node or pseudo node (where there is an attribute change)
Railway Linkset. This dataset is for named railways, in most cases these will be heritage or preserved railways such as the Bluebell Line but can also include named tram systems. There is a geometry dataset combining all of the Railway Links and also a cross reference lookup table
Railway Link features, as covered in the previous slide, include coverage of each non-heritage tram network within Great Britain. Further to this, however, information pertaining to a ‘presence of tram’ can be found via two additional ‘presence of tram’ data sources.
These simple enhancements are primarily intended to assist with utility and transport management, by easing the process of identifying tram-on-road extents.
Road Link features have been augmented with attribution relating to the presence, or otherwise, of tram tracks along their length. The primary attribute, here, is ‘presenceoftram_extentoflink’, which indicates whether a tram link continues along the links full length, just a part of it, or not at all.
In addition, there are also self-explanatory attributes for update date and data source.
Tram On Road features are created from the same geometry as Road Links but only the parts where tram line is present in the underlying topographic data. This means that as the entire Road Link is not present the Tram On Road Features do not form a network. The Tram On Road Features reference the underlying Road Link features.
This is a discrete collection of line features, as part of the wider Transport theme, that explicitly represent locations where tram tracks fall directly within highways. It features obvious cases where tram rails clearly follow along the direction of a road. However, it also includes instances where tram tracks cross directly over highways, in a manner that is analogous to conventional level crossings.
The OS NGD data comes in two formats, CSV and GeoPackage (GPKG)
The GeoPackage format comes ready to load into the GIS package of the users choice with different gpkg files for each layer.
The CSV format is more suited for loading into a database. It has all of the same layers in csv format and all the same attribution as the GeoPackage, however instead of storing the geometry in a GIS ready format, it is stored as a POINT, LINESTRING or MULTILINESTRING attribute with all of the vertices stored as co-ordinate pairs in the text file.
Links that may be useful:
This content has been developed from what was originally a Lightning Talk PowerPoint slide set. These slides are available to PSGA members to view and download from the PSGA members area of the OS website
