[OSM-talk] Funny Mapnik rendering of lakes

Jon Burgess jburgess777 at googlemail.com
Mon Aug 13 21:40:33 BST 2007

On Mon, 2007-08-13 at 20:27 +0100, Dermot McNally wrote:
> Hi Mapnik experts,
> Take a look at Lough Corrib on the Mapnik layer:
> http://www.openstreetmap.org/?lat=53.38802704172361&lon=-9.17438578308073&zoom=11&layers=B0F
> See the straight line along the west bank? It doesn't really exist,
> and I'm pretty sure that it wasn't like that at any point during the
> upload of the lake. (Doesn't JOSM upload all points, then define the
> segments and only then define the ways?)
> Maybe it'll just go away next time the area is rendered, but I mention
> it in case there's a bug.

 Looking at the intermediate Mapnik PostgreSQL DB shows the way
(id=5021907) as being made up of two short polygons plus a couple of
very long linestrings. I'll have to dig a little deeper to figure out
why this is happening. The data looks OK in JOSM (all 1852 segments of
it) but I've not looked too closely at it yet.

It could be a bug in the osm2pgsql code or one of the libraries it uses
or some non-obvious data problem.


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