On Sep 15, 2010, at 4:55 PM, Janes Huff wrote: > Hi, > I tried some tests with mapnik using osm data (download brandenburg.osm from > Geofabrik; cut out a smaller region with osm2pgsql: osm2pgsql --bbox > 12.6247,52.2599,13.3848,52.5194 -m -d gis brandenburg.osm). All parts > (postgis, mapnik, ...) seem to work fine. > > I created the two files: > > a) werder.py (origin code I took from here: > http://trac.mapnik.org/wiki/XMLGettingStarted): > > #!/usr/bin/env python > # -*- coding: utf-8 -*- > import mapnik > mapfile = 'werder.xml' > map_output = 'werder.png' > m = mapnik.Map(800, 600) > mapnik.load_map(m, mapfile) > bbox = mapnik.Envelope(mapnik.Coord(12.6247,52.2599), > mapnik.Coord(13.3848,52.5194)) > m.zoom_to_box(bbox) > mapnik.render_to_file(m, map_output) > Your Map is in mercator so you need to pass mercator coordinates to the zoom_to_box function.
Here is an example of reprojecting long/lat coords into spherical mercator: http://mapnik-utils.googlecode.com/svn/example_code/google_mercator_projection/world_mercator.py You can also just render the werder.xml with nik2img.py which will automatically zoom to the extents of your data (if set correctly, see below). > > b) werder.xml: > <?xml version="1.0" encoding="utf-8"?> > <!DOCTYPE Map> > <Map bgcolor="#ffffff" srs="+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 > +ellps=WGS84 +datum=WGS84 +units=m +no_defs"> > [...snip...] > > <Layer name="strassen" status="on" srs="+proj=merc +lon_0=0 +k=1 +x_0=0 > +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"> > <StyleName>strassen</StyleName> > <Datasource> > <Parameter name="type">postgis</Parameter> > <Parameter name="password">my-very-secret-pw</Parameter> > <Parameter name="host">localhost</Parameter> > <Parameter name="port">5432</Parameter> > <Parameter name="user">postgres</Parameter> > <Parameter name="dbname">gis</Parameter> > <Parameter name="table">planet_osm_line</Parameter> > <Parameter name="estimate_extent">false</Parameter> > <Parameter name="extent">12.6247,52.2599,13.3848,52.5194</Parameter> > </Datasource> > </Layer> > </Map> > Your layer is going to be in spherical mercator () as it was imported with the -m flag of osm2pgsql, so that means your extent value must also be in spherical mercator coordinates (not long/lat). An easy solution here is to let PostGIS calculate the layer's extents automatically (just remove the 'extent parameter' to trigger this). > After execution I get no error message and the PNG-file I waited for. Well, > but it's blank - sorry - it's background color is #fffff (or whatever color I > setted). But no map features are shown. > I searched a lot by now, but couldn't figure out the mistake. Could you give > me a hint, please? > > > Thank you, > CC > > > P.S.: > OS: Kubuntu 10.4 > Mapnik: 0.7 > Postgresql: 8.4 > Postgis: 1.5.1 > osm2pgsql: 0.66.20090526 > _______________________________________________ > Mapnik-users mailing list > [email protected] > https://lists.berlios.de/mailman/listinfo/mapnik-users
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