[OSM-dev] PostGIS & Mapnik problem

[Andy Allan]

On Wed, Jan 13, 2010 at 1:12 PM, Colm McMullan <colm.mcmullan at gmail.com> wrote:

> <Map bgcolor="#ffffff" 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 -tl -r">
>     <Style name="line style 2">
>         <Rule>
>                 <LineSymbolizer>
>                         <CssParameter name="stroke">#000000</CssParameter>
>                         <CssParameter name="stroke-width">3.0</CssParameter>
>                 </LineSymbolizer>
>         </Rule>
>     </Style>
>     <Layer name="layer 4" srs="+proj=latlong +ellps=WGS84 +datum=WGS84
> +no_defs" status="on">
>         <StyleName>line style 2</StyleName>
>         <Datasource>
>             <Parameter name="type">postgis</Parameter>
>             <Parameter name="host">localhost</Parameter>
>             <Parameter name="user">postgres</Parameter>
>             <Parameter name="dbname">gis</Parameter>
>             <Parameter name="estimate_extent">true</Parameter>
>             <Parameter name="table">planet_osm_roads</Parameter>
>         </Datasource>
>     </Layer>
> </Map>

>
> So I'm a bit stumped, what am I missing?  Has anyone got any suggestions?

My rule of thumb with Mapnik is "it's always a projection problem".
Are you sure that your db is in latlong? By default osm2pgsql is in
spherical mercator.

If that's not it, I'd suggest starting with the generate_image.py and
the osm.xml from OSM SVN, and get that working with all the defaults
as described on the wiki. You can then step through changes one at a
time (e.g. changing your db to latlong instead of spherical mercator,
using your own style instead of osm.xml and so on.

Cheers,
Andy