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

Jon Burgess jburgess777 at googlemail.com
Wed May 16 19:07:34 BST 2007


On Wed, 2007-05-16 at 16:15 +0100, Nick Black wrote:
> 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.

No not for navigation, but they are very useful for route planning. I
frequently find myself in the middle of central London asking myself
which is the best Tube station to walk to in order to get back to a
particular mainline station with minimum changes on the underground. 

Often it is faster to walk to a station on a line which gets to the
destination with no changes then it is to walk to the nearest station
and have to change lines. I curse the 'other map' that forces me to keep
flicking between the main map and the back cover in order to work this
out.


>   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.  
> 
Since you can not enter or leave the underground at any intervening
point, nor can you see it, I don't see why this is of too much
importance.

> 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. 

As you mentioned in another email, maybe we need to support overlays or
multiple alternate osm.xml files. Rendering mapnik tiles in real-time is
possible although i'm nervous that it would greatly increases the load
on tile. 

	Jon






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