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OS Open Rivers Technical Specification
This technical specification provides detailed technical information about OS Open Rivers. It is targeted at technical users and software developers.
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.
The identifier is not persistent between product versions; there is therefore no change-history information for features.
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:
| Stereotype | UML element | Description |
|---|---|---|
Application schema | Package | Parent package containing sub-packages and elements that comprise part of the modular specification. |
FeatureType | Class | A spatial object type [ISO 19136]. |
Type | Class | A structured data type with identity. |
CodeList | Class | A controlled set of values for a free text data type that may be extended. |
Voidable | Property | A property that is required but is either not currently captured (unknown) or is partially populated (unpopulated). |
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:
Generalisation/specialisation – This is used to denote either:
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
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.
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:
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