OpenStreetMap Forum

John Kroeker

Member

From: Vancouver BC

Registered: 2008-05-07

Posts: 6

Mapnik, Osmarender and coastal rivers using multipolygons

I've been trying to map a larger coastal river in my area, using a multipolygon with k=waterway and v=riverbank.  After a few iterations, I finally managed to get it to display correctly (well, almost ) on Information Freeway.   However, the main map rendered by Mapnik doesn't display the riverbank properly.

http://www.informationfreeway.org/?lat= … 89&zoom=12
http://www.openstreetmap.org/?lat=49.21 … 89&zoom=12

Since it's a coastal river, the riverbank is also tagged as coastline to a point.  Mapnik renders it properly to the point where the coastline ends, but where the riverbank area meets the coastline, the river is rendered as land.  Osmarender handles it the way I expect it to.   

Is this a bug in the way Mapnik renders a coastline/riverbank junction, or is there something I'm missing?

I've been looking at how other coastal rivers have been mapped to see if I can figure out what I've done wrong, but there doesn't seem to be a consistent way of doing it.  Some are tagged as natural=water, but this doesn't seem quite right since that tag is intended for lakes and other enclosed water from what I've read on the wiki.  Others are tagged as natural=coastline for the length of the river which doesn't seem right either.

John

emj

Member

From: .se (59.3N17.99E) 0735969076

Registered: 2006-06-18

Posts: 949

Re: Mapnik, Osmarender and coastal rivers using multipolygons

Have you solved it? Water is very tricky on Openstreetmap, always have been... I have tried to summerise everything that is used and suggest someting better but it's really hell...

John Kroeker

Member

From: Vancouver BC

Registered: 2008-05-07

Posts: 6

Re: Mapnik, Osmarender and coastal rivers using multipolygons

No, I haven't solve it yet.

I've checked a few other rivers since I my original post and I keep seeing the rivers defined as coastline or as water, as I mentioned. 

It makes sense to me that it should be perfectly acceptable for an area defined as waterway=riverbank to join with a  way defined as coastline, and that the junction should be rendered as water.

If it worked this way, I believe it would be a lot easier to draw rivers, since, as you say, it's really hell right now.

John

emj

Member

From: .se (59.3N17.99E) 0735969076

Registered: 2006-06-18

Posts: 949

Re: Mapnik, Osmarender and coastal rivers using multipolygons

Sigh. I don't see what is wrong. But to understand this you would have to

Check that mapnik really handles
* waterway=riverbanks
* multipolygons with that option.

That should be the problem, everything else seems to be correct (I can very well have missed something, I got nostalgic watching Vancouver instead of the map, it's a beautiful place).. ;-)

John Kroeker

Member

From: Vancouver BC

Registered: 2008-05-07

Posts: 6

Re: Mapnik, Osmarender and coastal rivers using multipolygons

I checked osm.xml in the Slippy Map and couldn't find any reference to riverbank, so there doesn't appear to be any support for waterway=riverbank.   

There a problem report in trac for this (#669).  I'm not sure about the response though, since it says that it's rendered properly in Mapnik at z13 to z17.  How can this be if there's no code to handle riverbank?

JRA

Member

Registered: 2007-12-17

Posts: 677

Re: Mapnik, Osmarender and coastal rivers using multipolygons

I tried to mark one larger river area as waterway=riverbank as described in suggested features a week ago or so.  Riverbank got rendered as closed line by Mapnik, not as water area.  I had to add natural=water to get it filled.

John Kroeker

Member

From: Vancouver BC

Registered: 2008-05-07

Posts: 6

Re: Mapnik, Osmarender and coastal rivers using multipolygons

I could do that, I guess.   Natural=water is intended for lakes though, so when you view it in Potlatch it shows as a lake, which just seems wrong.

Maybe I'm just being picky, but the right solution is to fix Mapnik to handle riverbanks properly.

emj

Member

From: .se (59.3N17.99E) 0735969076

Registered: 2006-06-18

Posts: 949

Re: Mapnik, Osmarender and coastal rivers using multipolygons

http://trac.openstreetmap.org/

That is where you report this.