[OSM-dev] MAPNIK - proposal to drop rendering of underground railway lines

Nick Black nickblack1 at gmail.com
Wed May 16 16:15:17 BST 2007

To clarify, by underground railways I mean railways that go under the
ground.  They cant be seen from the surface and so are not useful for
navigation.  Further, I'm not sure if the underground lines in London, at
least, should even be in OSM as they are just straight lines inbetween
stations and don't represent geometry.  The nodes should be in the db, but
the lines should be inserted by the renderer/editor or whatever client is
being used.

Trains that usually go overground but are temorarily diverted underground,
*could* be rendered - mainly for the sake of not having a gap in their
tracks on the map, which could not be distinguished from an acutal gap or
the end of the line.  However, I suspect that the resulting map would again
be too cluttered.

On 5/16/07, Robert (Jamie) Munro <rjmunro at arjam.net> wrote:
> Hash: SHA1
> Nick Black wrote:
> > I would like to stop Mapnik from rendering underground railway lines for
> > these reasons:
> >
> > 1) They make the map look cluttered
> > 2) They are not helpful as a navigational or locational aid
> > 3) They impede the use of the map as a navigational aid
> > 4) They are very innacurate, non-geometrical approximations, derived
> > from the location of stations
> +1 to removing underground railway lines if you mean "railway lines that
> are under the ground" (or replacing them with light-dotted lines or
> something).
> - -1 to removing underground railway lines if you mean "railway lines that
> belong to 'London Underground', some of which run above ground (e.g. in
> the suburbs)"
> I think the problem may be that it is not obvious what railway=subway is
> supposed to mean. Does this mean that the railway is in a tunnel, or
> just that it is managed by "London Underground" or similar? Map features
> says "A passenger rail service running mostly underground."
> What do we tag normal (mainline) train lines that are in tunnels?
> What do we tag "London Underground" lines that are above ground? Should
> we add tunnel=no to these? Or should we not assume tunnel=yes for
> railway=subway?
> Robert (Jamie) Munro
> P.s. would it be possible to use the right colours for underground
> lines, and move the parts that are actually under the ground to a
> transparent overlay? Or perhaps the overlay could have the colours, but
> without it, the overground parts just show as railway lines an normal.
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Nick Black
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