[OSM-talk] Large Rivers in general, mapnik rendering in Particular

[Artem Pavlenko]

On 8 Feb 2008, at 11:26, Andy Allan wrote:

> On Feb 8, 2008 11:09 AM, Artem Pavlenko  
> <artem.mapnik at googlemail.com> wrote:
>
>> We can make osm2pgsql or coastline tools to create polygons, but why
>> not create them in the first place ?
>> Can someone enlighten me, please ?
>
> If I wanted to draw the rivers as light blue* with dark blue
> riverbanks, wouldn't storing them as polygons would make this hard? I
> don't think it would be easy to work out which sections of the
> polygons are where the river continues as opposed to being the
> riverbank.

OK, valid point.
>
> If we store the riverbanks, then we can pre-process to our hearts
> content using osm2pgsql and the like. That way I could have riverbanks
> as polylines and rivers as polygons and render them as I see fit. The
> pre-processing could work very similarly to the coastlines, using a
> left- or right-hand side rule and continuing the riverbank where one
> way joins onto the next to construct the polygons required.

Can relations help here ?
>
> Cheers,
> Andy
>
> * As I think more and more about contours, and semi-transparent
> renderings and so on I realise that most area-fills will be
> translucent with edges on my maps, so we need to avoid abutting
> polygons if we aren't intending to represent an edge.