Wikipedia:WikiProject Geographical coordinates/Linear

There are a number of ways in which linear referencing (coordinate referencing for linear features) can be added to Wikipedia. As yet, there is no single method which has achieved consensus.

The best method may depend on the type of feature, its length, and the number of significant points of interest along it (though such points need not be sufficiently notable as to warrant their own article).

What are linear features

Linear features include, but are not limited to:

• Tracks, trails, etc.
• Roads
• Railway lines
• Bridges
• Tunnels
• Canals
• Borders
• Rivers
• Valleys
• Mountain ranges

Options

Editors may give:

• One pair of coordinates, for the mid point
• One pair of coordinates, for the most significant point (e.g. the estuary or mouth of a river)
• Two pairs of coordinates, one for each end
• Three pairs of coordinates, combining the above
• Multiple coordinates, for points of interest
• No coordinates

Main coordinates

In any of the above cases, which involve more than one pair of coordinates, a single (or "main") pair may be used as the coordinates for the whole article (and for its inclusion in partner sites such as Google Maps).

A "main" coordinate may not be appropriate for very long features; the definition of "very long" in this context is yet to be determined.

Flexibility is needed in order to label a representative point. For example, a canal's "main" coordinates may be best given as a point where it is a body of water; a nearby location may be better than a midpoint occupied by a notable or atypical object such as a tunnel or causeway.

Solutions

• Whole article as table:
  • List of crossings of the River Severn
• Table in article (non-collapsible):
  • Netherton Tunnel Branch Canal
• Table in article (collapsible):
  • Tame Valley Canal
• Mouth of river:
  • River Trent
• Both end points; plus middle as "main" coordinates:
  • Severn Tunnel
• Each end:
  • Channel Tunnel

Templates

These templates may be useful:

• {{coord}} - for each point's coordinates
• {{kml}} - maps of all coordinates; coordinates as KML download; etc.

Draft recommendations

feature	main coordinates 1	further recommended coordinates 2	optional additions3	examples
bridge	midpoint5	both ends	features crossed, support pillars	Astoria–Megler Bridge
canal	midpoint5	both ends	junctions, wharves, crossings, locks
unburied pipeline	midpoint5	endpoints	pumping stations, junctions, major changes in direction
buried pipeline	one endpoint	other endpoint and midpoint5	pumping stations, exposed sections
railway	midpoint5	both ends	stations, former stations, junctions, significant bridges
river	estuary/mouth	source, major confluences	crossings, other confluences, boundaries crossed, weirs, major changes in direction, islands	Johnson Creek (Willamette River)
road	midpoint5	both ends	major towns visited, major junctions, major features crossed	M6
tunnel	one endpoint	other endpoint and midpoint5	ventilation shafts	Robertson Tunnel
valley	central point	both ends	watersheds, rivers, settlements, landmarks, features

Notes:

1. See above.
2. For very short features (e.g. a small bridge) just the mid-point will suffice.
3. For very long features, only major points of interest should be included.
4. Route is a series of paths, as in a highway route. Or a long distance hiking trail, a series of individual trails which (usually) connect. To be unambiguous, the point must not be near any intersection
5. "Midpoint" is not meant to be strictly the mathematical midpoint, but a representative point of the feature near its middle. If this should fall in a non-representative portion, the coordinate point chosen should be moved further toward one end. If the midpoint of a highway falls at an intersection with another highway, the coordinate chosen should be moved some distance from the intersection so that the other highway is not misinterpreted as the feature. Likewise, a highway portion which splits into two streets (as in an urban one way grid) should not be used as the selected point unless that is representative of the feature.

Precision

Coordinates for points on linear features should use a high level of precision, commensurate with features' small width, not great length, to ensure that the points are centred on, not merely near, the feature.

Out of scope

This guideline is not intended to cover:

• Polygons (i.e. country or county outlines) (e.g. Italy, Texas Coastal Bend)
• Lines of latitude or longitude.
• Forked, branched or other irregular features
• Non-linear collections of points of interest (e.g. "all cathedrals in England")

See also

Wikipedia:WikiProject U.S. Roads/Maps task force/Tutorial#Creating a KML file