[OSM-dev] Tricky problem rendering tiles (coastline incomplete)

Kay Drangmeister kay at drangmeister.net
Wed Jan 25 23:12:25 GMT 2012

Hi all.

I have a rendering problem that I am desparately trying to hunt down.
Please have a look at low zoom tiles (I use the (modified for b/w) original
osm stylesheet, the newest one, for mapnik 2.0). Of course I use mapnik2
as well.

Z0: http://drangmeister.net/osm/wz0.png
Z1: http://drangmeister.net/osm/wz1.png
Z2: http://drangmeister.net/osm/wz2.png

Look at parts of Australia missing. I confirmed it has nothing to do
with recent remapping efforts in that area :-)

Zooming to Fiji at Z4: http://drangmeister.net/osm/wz4.png you see that
the islands are missing.

Zooming further in to Z10 they appear: http://drangmeister.net/osm/wz10.png

So it looks as if there's a vertical strip worth about 1 tile wide around
the 0° / 360° longitude that is not rendered, independent of the zoom. I.e.
at Z0 halve australia is missing, at Z4 only Fiji and NZ is missing, at
Z10 only maybe an island of Fiji is missing.

Here is the relevant part of the stylesheet for rendering:

<Style name="world">
       <PolygonSymbolizer fill="#eeeeee"/>

<Layer name="world" status="on" srs="+proj=merc +a=6378137 +b=6378137
+lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null
+no_defs +over">
       <Parameter name="type">shape</Parameter>

If I rename shoreline_300.shp away then I cannot render anything due
to errors, so it's the correct file being used.

It also appears to be no problem of the database, because as with Fiji,
the data is there, just not being rendered in Z4.

Is there a "render bounding box" somewhere I don't know, maybe in tirex?
There's nothing suspicious in the /etc/tirex config files.

Kind regards,

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