OS Open Rivers consists of two core features:

1. WatercourseLink – A feature which represents all or part of a watercourse.

2. HydroNode – A feature which represents a river’s source, end, or where three or more links meet at a junction, and places where the real-world related attribution recorded changes, for example, a watercourse becoming tidal.

This product is based upon the INSPIRE Data Specification on Hydrography. The result is a product that inherits attribution from INSPIRE. An overview of the product's structure can be found in Figure 3 below, which highlights the inherited INSPIRE feature types and attribution. Properties of the INSPIRE specification which are voidable are not included in the diagrams or tables that follow. For information on the INSPIRE properties which are not included in this product, please see the INSPIRE Data Specification on Hydrography.

HydroNode features are added at the start and end of every WatercourseLink feature. They can represent the source of a watercourse, the end of a watercourse, a junction along a watercourse, or a change of real- world related attribution.

HydroNode

A feature at the end of one or more WatercourseLink features that indicates either the confluence or two or more watercourses and/or a change in the attribution of the WatercourseLink features.

hydroNodeCategory «voidable»

Nature of the HydroNode.

• Attribute name: hydroNodeCategory (GML), hydro_node_category (VectorTiles), hydro_node_category (GeoPackage), formOfNode (Esri shapefile)

• Type: HydroNodeCategoryValue

• Multiplicity: [1]

geometry

The location of the HydroNode.

• Attribute name: geometry (GML), Not provided (VectorTiles), Not provided (GeoPackage), Not provided (Esri shapefile)

• Type: GM_Point

• Multiplicity: [1]

This section describes the two features available in the OS Open Rivers product. The attributes associated with these feature types are listed below along with a brief description of their data properties.

Feature type attribute information

Name and Definition

The name of the attribute and what it is describing.

Attribute type

The nature of the attribute, for example, a numeric value or a logical indicator.

Multiplicity

Describes how many times this element is expected to be populated in the data. An attribute may be optional or mandatory within the product. These are denoted by:

• ‘1’ – There must be a value.

• ‘2’ – There must be two values.

• ‘n’ – There may be one or more values.

• ‘0’ – Population is optional.

These values may be used in combination.

• Association – An association identifies the relationship between features. These relationships are by reference only and the value will be the identifier of the referenced feature.

OS Open Rivers provides a two-dimensional, topologically-structured link-and-node network of Great Britain’s watercourses. A link represents the approximate central alignment of a watercourse. Links have been digitised in the direction of water flow. Attribution indicates the flow direction and name of each watercourse.

OS Open Rivers is a generalised product which is automatically derived from Ordnance Survey large-scale data. Generalisation is the process of reducing the scale and complexity of map detail whilst maintaining the important elements and characteristics of the features.

Available formats

OS Open Rivers is supplied in the following formats:

• Geography Markup Language (GML): A national vector dataset in GML 3.2.1 Simple Features Profile – level 0.

• Shapefile: A national vector dataset in Esri shapefile (.shp) format.

• GeoPackage: A national vector GeoPackage (.gpkg) file.

• Vector tiles: A national vector tiles file in MBTiles format.

Identifiers

Each feature has a unique identifier. The identifier property name, which holds the feature's unique identifier, differs for each format:

• GML: gml:identifier property.

• Esri shapefile: identifier property.

• GeoPackage: id property.

Adherence to standards

OS Open Rivers is based on the INSPIRE Data Specification on Hydrography, which itself is based on the ISO/TC 211 family of open standards.

Extension of the INSPIRE specification

OS Open Rivers extends the INSPIRE specification by extending the INSPIRE WatercourseLink feature type with a number of additional properties.

UML diagram and table conventions

The data structure is described by Unified Modelling Language (UML) class diagrams and accompanying tables containing text. The UML diagrams conform to the approach specified in ISO 19103 - Conceptual schema language and ISO 19109 - Rules for application schema, as adopted by INSPIRE.

Colour conventions are used in the diagrams and tables to distinguish the INSPIRE specification from the additional properties that have been added in the Ordnance Survey specification.

In the UML diagrams, classes from the INSPIRE data specification are grey, whereas classes in the Ordnance Survey specification are orange. All code lists are blue and enumerations are green (see diagram below) The accompanying tables use orange for feature types, blue for code lists, and green for enumerations.

Lexical conventions

• Class names are conceptually meaningful names (singular noun) in UpperCamelCase.

• Class names end in Value where the class is assigned the stereotype <<CodeList>> or <<Enumeration>>.

• Property names (attributes and associations) are in lowerCamelCase.

Stereotypes

The following stereotypes are used on UML elements:

Relationships and associations

There are four key types of relationship that can be defined between classes, only the following two exist in OS Open Rivers:

1. Generalisation/specialisation – This is used to denote either:

   1. An extension relationship - The target class represents the same real-world phenomenon. It has the same name as the class it extends. It simply includes additional properties. OR

   2. A sub-typing relationship - The target class defines a specialised sub-type of a parent feature, for example, a TransportNetwork is a sub-type of a generic Network class.

2. Directed association – This is used to denote relationships between features. These relationships are by reference only (that is, they are implemented by a property whose value is the identifier of the related feature or object). The directed end is assigned a name that describes the relationship and a multiplicity.

Index

This technical specification includes the following sections:

• Product structure

• Feature types

• Code lists

• GML overview

• ESRI shapefile overview

• GeoPackage overview

• Vector tiles overview

A code list is a controlled set of values for an attribute. This section identifies the code lists used within OS Open Rivers and describes their values.

The WatercourseLink feature is a generalised representation of the watercourse alignment. WatercourseLink features are split where their real-world related attribution changes or where they meet to form a junction.

WatercourseLink attributes

A segment that forms part of a watercourse.

flowDirection «voidable»

Direction of water flow in the segment relative to digitisation of segment geometry.

• Attribute name: flowDirection (GML), flow_direction (VectorTiles), flow_direction (GeoPackage), flow (Esri shapefile)

• Type: LinkDirectionValue

• Multiplicity: [1]

length «voidable»

Length of network segment.

• Attribute name: length (GML), length (VectorTiles), length (GeoPackage), length (Esri shapefile)

• Type: Length

• Multiplicity: [1]

centrelineGeometry

The geometry that represents the centreline of the link.

• Attribute name: centrelineGeometry (GML), Not provided (VectorTiles), Not provided (GeoPackage), Not provided (Esri shapefile)

• Type: GM_Curve

• Multiplicity: [1]

fictitious

Indicator that the centreline geometry of the link is a straight line with no intermediate control points – unless the straight line represents the geography in the resolution of the data set appropriately.

• Attribute name: centrelineGeometry (GML), Not provided (VectorTiles), Not provided (GeoPackage), Not provided (Esri shapefile)

• Type: Boolean

• Multiplicity: [1]

form «voidable»

Classification of the type of watercourse that is formed by the WatercourseLink.

• Attribute name: form (GML), form (VectorTiles), form (GeoPackage), form (Esri shapefile)

• Type: WatercourseFormValue

• Multiplicity: [1]

watercourseName

Recognised name assigned to the watercourse.

• Attribute name: watercourseName (GML), watercourse_name (VectorTiles), watercourse_name (GeoPackage), name1 (Esri shapefile)

• Type: LocalisedCharacterString

• Multiplicity: [0..1]

watercourseNameAlternative

An alternative name of the main watercourse the link is part of. Note 1: The language used to define the name shall also be provided as a three-digit ISO 639-2 code ('eng', 'cym' 'gla').

• Attribute name: watercourseNameAlternative (GML), watercourse_name_alternative (VectorTiles), watercourse_name_alternative (GeoPackage), name2 (Esri shapefile)

• Type: LocalisedCharacterString

• Multiplicity: [0..1]

startNode

The HydroNode coincident with the first vertex for this WatercourseLink.

• Attribute name: startNode (GML), Not provided (VectorTiles), start_node (GeoPackage), startNode (Esri shapefile)

• Multiplicity: [0..1]

endNode

The HydroNode coincident with the last vertex for this WatercourseLink. On very rare occasions, the end HydroNode may be the same instance as the start HydroNode.

• Attribute name: endNode (GML), Not provided (VectorTiles), end_node (GeoPackage), endNode (Esri shapefile)

• Multiplicity: [0..1]

OS Open Rivers is supplied as an Esri shapefile. Shapefile is an open file format to store geometry and attribute information about spatial features.

Attribute mapping

The naming of attributes between GML and Esri shapefile is different; shapefiles limit attribute names to 11 characters, whereas GML has no limit. The tables that follow map the GML attribute name to its Esri shapefile equivalent for the WatercourseLink and HydroNode features.

The WatercourseLink feature is attributed with a form with a data type of WatercourseFormValue. The following table lists the codes which are used to populate this field and gives a description for each code.

Code list: WatercourseFormValue

Classification value defining the type of WatercourseLink

This section describes the GML format for OS Open Rivers. We recommend that you read this section in conjunction with the Open Geospatial Consortium (OGC) document, OpenGIS® Geography Markup Language (GML) Encoding.

The XML specifications on which the GML is based are available from the World Wide Web Consortium (W3C) website: https://www.w3.org/XML/.

Information about Unicode and UTF-8, the character encoding that we use, is available on the Unicode Consortium website: http://www.unicode.org/.

Schema overview and location

XML schemas are used to define and validate the format and content of the GML. The GML v3.2.1 specification provides a set of schemas that define the GML feature constructs and geometric types. These are designed to be used as a basis for building application-specific schemas, which define the data content.

The Ordnance Survey application schema, OSOpenRivers.xsd, which is referenced by the data, is available on the OS Open page of the XML file resources section of our website.

It OS schema imports the INSPIRE Data Specification on Hydrography application schema, which in turn imports the GML 3.2.1 schemas. These in turn import schemas produced by the W3C, which are available from the W3C website at: http://www.w3.org/XML/1998/namespace.html.

All these schemas are defined in XML Schema Definition language (XSD), as defined by the W3C.

The OS application schema uses the XML namespaces detailed in the table below. A link to each definition is provided in the last column.

Simple Features Profile – Level 0

OS Open Rivers conforms to GML 3.2.1 Simple Features Profile – Level 0.

GML is designed to support a wide variety of capabilities, ranging from simple contextual mapping, such as OS OpenMap, to products that include complex geometric property types and even spatial and temporal topology. The Simple Features Profile of GML 3.2.1 defines a restricted subset of GML, which allows for greater interoperability.

The WatercourseLink feature is attributed with a flowDirection with a data type of LinkDirectionValue. The following table lists the codes which are used to populate this field and gives a description for each code.

Code list: LinkDirectionValue

List of values for directions relative to a link http://inspire.ec.europa.eu/codelist/LinkDirectionValue/

Where the flow direction has not been determined, this attribute is set to null and a nilReason is given.

• Where the value of nilReason is set to unknown, then the flow direction is not known to Ordnance Survey. A correct value may exist, but the methods employed by Ordnance Survey to date have not facilitated capture.

• Where the value of nilReason is set to missing, then the flow can be considered indiscernible. Ordnance Survey has attempted to identify the flow on the ground, but no flow has been determined.

The feature is attributed with a hydroNodeCategory with a data type of hydroNodeCategoryValue. The following table lists the codes which are used to populate this field and gives a description for each code.

Code list: HydroNodeCategoryValue

Classification value defining the type of hydrographic node

Where the hydroNodeCategory has not been identified, this attribute is set to null and a nilReason of inapplicable is given. This will indicate where an attribute of the watercourse changes which requires a watercourseLink to split, for example, watercourseName. In the Esri shapefile, these are given the attribute value of pseudo.

The Open Geospatial Consortium (OGC) defines GeoPackage (*.gpkg) an open, non-proprietary, platform- independent, standards-based data format for geographic information systems (GIS). It is designed to be a lightweight format that can contain large amounts of varied and complex data in a single, easy-to-distribute and ready-to-use file. GeoPackage is natively supported by numerous software applications.

GeoPackage offer users the following benefits:

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

• Attribute names are not limited in length, making the format user friendly.

• The file size limit is large at 140 TB.

• It supports raster, vector, and database formats, making it a highly versatile solution.

• It is an OGC standard.

• In most cases, it is a plug-and-play format.

For information on how to open, use and understand a GeoPackage dataset, please refer to our guide. For further information on GeoPackage, please see the .

OS Open Rivers is supplied as a national GeoPackage file.

Attribute mapping

The naming of attributes between GeoPackage and GML is very similar as both formats do not limit the number of characters for an attribute name. The following tables map the GML attribute name to its GeoPackage equivalent for the WatercourseLink and HydroNode features.

OS Open Rivers is supplied as a national vector tileset in a single MBTiles file. This is a lightweight set of tiles that is efficient and fast to render in your software, provides high-resolution data and a seamless experience when zooming in and out. The data is supplied in Web Mercator projection (ESPG:3857).

Attribute mapping

The naming of attributes between vector tiles and GML is very similar as the vector tiles (set within the MBTiles file) do not limit in the number of characters for attribute names. The tables included here map the GML attribute name its vector tiles equivalent for the WatercourseLink and HydroNode features.

In April 2023 there were significant changes to the naming patterns in the GeoPackage format. The formatting of most names changed from title case to snake case. The following tables map the previous names to those use after April 2023.

Attribute names

Layer names

Column names

Constraints

The vector tiles schema, as well as the zoom level for each attribute, is detailed in the following table.

watercourse_link attributes

hydro_node attributes