[OSM-talk] River Avon in Mapnik

[David Groom]

> ----- Original Message ----- 
> From: "David Groom" <reviews at pacific-rim.net>
> To: "mike" <mike at bristolbeat.co.uk>; <talk at openstreetmap.org>
> Sent: Tuesday, October 23, 2007 11:11 AM
> Subject: Re: [OSM-talk] River Avon in Mapnik
>
>
>
> It depends on how you see things but it could be both a tagging and a 
> rendering problem.
>
> The riverbank was originally derived from the PGS coastline import script, 
> and the data then tidied up by me.
>
> The import script tagged the riverbanks as natural=coastline, and I left 
> it as such for two reasons:
>
> 1) no clear definition of where a coastline ends and a river begins when 
> it is a tidal river.
>
> 2) In Osmarender the rendering of coastline areas in my opinion is a lot 
> less problematic than rendering of river areas, with a coastline all you 
> have to do is ensure the "segments" point the right way, with water on the 
> right,

I should have added a point (3)

3)  To get an area waterway = riverbank rendered in mapnik it has to be a 
closed area. This means drawing a "segment" across the river to join each 
side of the riverbank.  I know this will render correctly, but it seems 
"wrong" to me to mark a riverbank across the river when no such feature 
exists in real life.  I guess it depends on whether you see the data we are 
producing as being tagged to draw pretty maps in mapnik, or to actually 
represent what exists in real life.

As I said earlier, I rather hope relations might solve the problem.


>
> However Mapnik ignores all natural = coastline tags, as it generates the 
> coastline from I believe a modified version of the original shapefiles.
>
> I'm rather hoping that when the relations concept is a bit more developed 
> that the rendering of wide rivers might be improved, and be more 
> consistent between mapnik and osmarender.
>
> David
>
>  ----- Original Message ----- 
>  From: mike
>  To: talk at openstreetmap.org
>  Sent: Tuesday, October 23, 2007 10:29 AM
>  Subject: [OSM-talk] River Avon in Mapnik
>
>
>  I just noticed the river avon is not rendered correctly in mapnik, from 
> bristol channel down to the harbour:
>
>  http://www.openstreetmap.org/?lat=51.4614&lon=-2.6407&zoom=13&layers=B0F
>
>  Osmarender does a much better job in this instance.
>
>  I wonder if this is a tagging issue or a rendering problem?
>
>  mike