[Talk-transit] [Spam] Re: Multiple tracks

Peter Miller peter.miller at itoworld.com
Wed Jun 24 19:20:31 BST 2009


On 24 Jun 2009, at 15:11, Frankie Roberto wrote:

> On Wed, Jun 24, 2009 at 2:45 PM, Richard Mann <richard.mann.westoxford at googlemail.com 
> > wrote:
>
> Do relations solve the problem at all? If a track is part of a route  
> relation, then could a renderer use that as a means of aggregating  
> the tracks together?
>
> My hunch is that relations probably don't actually help much, unless  
> you could rely on them being done consistently and accurately.
>
> Hmm...
>
> One idea another OSMer suggested a while back (when the idea of  
> tagging tracks still sounded ridiculous) is to have some way of  
> distinguishing between a 'track' and a railway line (or 'corridor'  
> is perhaps a better word), so that renderers can choose which to  
> display (and so that the data contains both conceptually different  
> things).
>
> Not sure how best to implement this. The easiest thing would be to  
> have the middle track double up as the way which represents the  
> line, somehow. The hardest thing might be to have ways which mark  
> both edges of the rail corridor (like how we do riverbanks).

I would suggest that renderers should taker advantage of the fact that  
as one zooms out then the different tracks are so close together that  
it doesn't really matter in most cases which one it draws and it can  
normally choose one at random to draw. As a refinement the relation  
could identify the preferred track using a 'role' to say 'draw this  
one' for situations where the geometry is very different for the  
various ways.

Similarly Junction relations would soak up all the fiddly tracks at  
junctions and replace them with one point (and the junction relation  
includes an optional 'hint' location to show where it should go).

The selected track is then drawn from the starting junction (using the  
location of the junction node rather than the first point on the  
track) to the end junction taking via points from the selected way.

This section of track from Finsbury Park through Harringay, Hornsey to  
the junction past Aexandra Park might be a good test route to try any  
of our proposals. Here is an image showing an overlay for the proposed  
simplified rendering where there is only a single stroke drawn to  
cover all of the individual tracks.
http://www.flickr.com/photos/peterito/3657058971/



Regards,



Peter


>
> Frankie
>
> -- 
> Frankie Roberto
> Experience Designer, Rattle
> 0114 2706977
> http://www.rattlecentral.com
>
> _______________________________________________
> Talk-transit mailing list
> Talk-transit at openstreetmap.org
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