[OSM-talk] Mapnik rendering artifacts

[Artem Pavlenko]

On 30 Jan 2008, at 12:41, Karl Newman wrote:

> I'm seeing faint gray lines on the main site slippy map Mapnik base  
> layer, and I'm at a loss to explain their source. At first I  
> thought they were state borders, but I'm seeing the lines running  
> through the middle of states, too (here http:// 
> www.openstreetmap.org/?lat=42.001&lon=-120.048&zoom=9&layers=B0FT  
> it runs vertically through the middle of Oregon). Then I thought  
> they were tile boundaries, but that's not consistent, either. Even  
> weirder is on the California-Nevada border, there are two vertical  
> lines right next to each other, not always parallel. (See here:  
> http://www.openstreetmap.org/? 
> lat=41.62&lon=-120.053&zoom=9&layers=B0FT). I downloaded that area  
> in JOSM but all I saw was a single state border way. It doesn't  
> seem to have a source in the OSM data, so maybe it's something  
> caused by the conversion to pgsql or by the renderer itself (maybe  
> a projection issue)? I don't think it's related to the recent  
> mod_tile changes, because as far as I know that only affects how  
> the tiles are stored and served, not how they're rendered. (If I've  
> said something stupid, please forgive me. I *think* I understand  
> the process...)
>
> Any thoughts, anyone?
>
> Karl

Ok, I got it. There are artifacts from rendering adjacent coast-line  
polygons (which are tiled -  100x100km squares inland)
This will be fixed when we upgrade to new coastline shape files - new  
tiles overlap by 150m and don't have these faint lines

Artem

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