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

Artem Pavlenko artem at mapnik.org
Wed May 16 19:24:12 BST 2007


On 16 May 2007, at 19:07, Jon Burgess wrote:

> 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
>


How about even paler grey dashed stroke with the lowest z-order  
(-999999) and only rendered at high zoom levels ?

Cheers,
Artem


>
>
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Artem Pavlenko
http://mapnik.org



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