Tag:waterway=link
 waterway = link
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A virtual (topological) connection in the waterway network over a body of water, to enable routing through the waterway network. 
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| Group: waterways |
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| Status: in use |
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The tag waterway=link is used on ways to create a topological connection in the waterway network over the surface of a body of water. A typical use case is a way connecting an access point on a riverbank to the river's centerline. This connects the land routes with the water routes, and enables watercraft (and multi-modal) routing.
Unlike most waterway=* values, the tag does not model a discrete physical feature and does not imply a flow direction.
Background
A waterway network is similar to a highway network. In order to enable boat routing, features that are connected in real life need to be connected topologically in the data. The waterway=link allows mappers to specify routable connections over the surface of bodies of water in cases where no other waterway=* value is appropriate.
The most common use case for waterway=link is the connection between waterway centerlines and access points on land. This enables the full mapping of route=canoe water trail relations as a string of ways connected end-to-end. It also enables multi-modal routing. For example, a router could show someone how to access a backcountry campsite on an island by directing them to a public slipway, and then giving them boat directions for the remainder of the trip.
This tag was inspired by footway=link.
How to map
Create a way connecting two features within a body of water, usually an access point and a waterway=* feature, following the shortest reasonable path. Tag the way as waterway=link.
Add the appropriate water access tags to indicate which modes of transport are allowed and possible over the link. For example: access=*, boat=*, motorboat=*, canoe=*, sailboat=*, swimming=*. The access should be defined for the given section of the waterbody, not the endpoints.
Useful combinations
- Flow direction:
oneway=*indicates the water flow direction, if applicable. Most links have no appreciable flow. Note that flow lines should instead be mapped withwaterway=flowline. - Travel direction: namespaced access tags like
oneway:boat=*indicate direction restrictions for watercraft, if any. This encompasses both legal and practical restrictions (like strong currents). Most links allow bidirectional travel. - Attributes of the water body:
tidal=*,intermittent=*. Useful to notify users of potential hazards.
When not to use
Do not use waterway=link when modeling:
- Overland links between waterways: use
portage=* - Public transport routes: use
route=ferry - Marked navigation routes: use
waterway=fairway - Flow lines: use other
waterway=*values; in particular,waterway=flowlinemay be useful for linear representation of flows within a body of water mapped as an area (e.g. a lake or a reservoir).
Examples
- 1225286930
1225286930 – Canoe and motorboat link - 1214418034 1214418034 – Canoe portage link
Rendering
General-purpose maps need not render waterway=link. Marine transport maps may render the tag similar to other navigable waterways based on access tags.
Old tagging
The tag waterway=portage has previously been used by some mappers for the same purpose as waterway=link. However, this tag has been a source of confusion, with other mappers using waterway=portage for the portage path itself. The link value is more versatile than portage, which implies hand-carrying.