Feature types in the product

OS MasterMap Water Network Layer features are classified into feature types. Each feature type has associated attribution, and further detail can be found in the OS MasterMap Water Network Layer Technical Specification.

The product has two core feature types: WatercourseLink and HydroNode.

WatercourseLink Feature Type

A WatercourseLink feature represents the alignment of a watercourse; the majority have been derived from Ordnance Survey's detailed topographic data, made available to customers as the

OS MasterMap Topography Layer product.

WatercourseLink features are split in the following circumstances:

• Where two or more watercourses meet

• Where the real-world-based attribution of a watercourse changes

• Where the name of a watercourse changes or ceases to apply

WatercourseLink features are not split where they pass under or over one another at different levels. They may be split where they pass into a culvert or tunnel or onto an aqueduct.

Height has been added to each vertex coordinate using the raw data used to create the OS Terrain height products.

The WatercourseLink feature represents the alignment of watercourses.

HydroNode Feature Type

A HydroNode feature explicitly represents the source, sink or junction of a watercourse. In addition, they record the location where any real-world-related attribution changes.

A HydroNode feature may only exist at the end point of a WatercourseLink feature. Height has been added to the coordinate for the HydroNode using the raw data used to create the OS Terrain height products.

The HydroNode feature explicitly represents a watercourse's source and sink, and locations where junctions of watercourses exist.