Thanks Jon and Michal!
Using a shapefile without Antarctica worked just fine for me, thanks to Dane
S. the link is here:
http://mapnik-utils.googlecode.com/svn/trunk/sample_data/
I did attempt to reproject the Shapefile using MapWindow, but the program
fails during the conversion process. If someone knows of a better way to
reproject the TM shapefile, please let me know. Alternatively, if there are
shapefiles out there that have already been converted to mercator a link
would be great.
Thanks a bunch all!
On Mon, Oct 13, 2008 at 7:17 PM, Michal Migurski <[EMAIL PROTECTED]> wrote:
> I've seen this particular problem with this projection and shapefile
> numerous times.
>
> The reliable way I've found to deal with it has been to remove
> Antarctica. =\
>
> -mike.
>
> On Oct 13, 2008, at 3:51 PM, Jon Burgess wrote:
>
> > On Mon, 2008-10-13 at 18:24 -0400, Filipe Fortes wrote:
> >> Hello All,
> >>
> >> I'm just starting out with Mapnik and having an issue trying to
> >> duplicate the mercator projection used in Google Maps.
> >>
> >> I've taken the Hello World example from the map and modified it to
> >> use
> >> a different projection:
> >>
> >> #!/usr/bin/env python
> >> from mapnik import *
> >> projection = '+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 [EMAIL PROTECTED]
> >> +no_defs +over'
> >> m = Map(600,300,projection)
> >> m.background = Color('steelblue')
> >> m.srs = projection
> >> s = Style()
> >> r = Rule()
> >> r.symbols.append(PolygonSymbolizer(Color('#f2eff9')))
> >> r.symbols.append(LineSymbolizer(Color('rgb(50%,50%,50%)'),
> >> 0.1))
> >> s.rules.append(r)
> >> m.append_style('My Style',s)
> >> lyr = Layer('world')
> >> lyr.datasource = Shapefile(file='shapefiles/world_borders')
> >> lyr.styles.append('My Style')
> >> lyr.srs = '+proj=latlong +datum=WGS84'
> >> m.layers.append(lyr)
> >> p = Projection(projection)
> >> lower_left_xy = p.forward(Coord(-180.0, -45.0))
> >> upper_right_xy = p.forward(Coord(180.0, 80.0))
> >> bbox = Envelope(lower_left_xy,upper_right_xy)
> >> m.zoom_to_box(bbox)
> >> render_to_file(m,'images/world.png', 'png')
> >>
> >> I've attached the output -- as you can see, it's only rendering a
> >> subset of the countries, and I can't find any rhyme or reason why
> >> only
> >> those countries are showing up.
> >>
> >> I've also switched and used the TM world borders shapefile [1] --
> >> which renders exactly the same with the exception of also rendering
> >> the US. If I go back to using the latlong projection, this problem
> >> disappears.
> >>
> >> I'm guessing there's something basic I'm missing here, so I
> >> appreciate
> >> any one taking the time out to help a newbie :)
> >
> > That looks like the sort of issue that can happen when you deal with
> > projecting data at or very close to the 'edge' of the world. Problems
> > happen when the extremes of the bounding box in one projection wrap
> > when
> > projected to another. I had this with OSM shapefiles:
> >
> https://lists.berlios.de/pipermail/mapnik-devel/2007-September/000236.html
> >
> > Try:
> > - reducing the +-180 in the Coord() to say +-179
> > - check the extent on the shapefile (shpinfo will give you this)
> >
> > You may need to clip the edges of your shapefile very slightly (again
> > try +-179 to see if that helps). 1 degree is overkill but should
> > demonstrate if this helps.
> >
> > The more reliable solution is to convert your shapefiles to match the
> > map projection and then use these in Mapnik. Avoiding the reprojection
> > during the rendering is key.
> >
> > Jon
> >
> >
> > _______________________________________________
> > Mapnik-users mailing list
> > [email protected]
> > https://lists.berlios.de/mailman/listinfo/mapnik-users
> >
>
> ----------------------------------------------------------------
> michal migurski- [EMAIL PROTECTED]
> 415.558.1610
>
>
>
> _______________________________________________
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>
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