[OSM-talk] Mapnik rendering artifacts

[Karl Newman]

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
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