David, if your Mapnik Map srs is Spherical Mercator (which it looks to be) then you need to pass spherical coordinates to map.zoom_to_box().
A good way to confirm this is to call map.zoom_all() then print out the value for map.envelope() and see that the coordinates are in spherical mercator. If you need help converting see: http://mapnik-utils.googlecode.com/svn/example_code/google_mercator_projection/world_mercator.py Dane On Feb 15, 2011, at 9:47 AM, David Wiesen wrote: > Hi Dane, > > Thanks for the response. Unfortunately this doesn't seem to solve my issue. > In fact > when I specify epsg:4326 my tiles come up empty (meaning none of the shapes in > my shapefile appear in the tiles) > > For the tile I have been testing with, the details are > > 256x256 map, using the xml file and shapefile I attached. > bounding box = > Envelope(-122.183074951,37.4770377967,-122.18170166,37.4781276287) > > there are a number of shapes in my shapefile that should fall within that > bounding box > (when I load my shapefile into Google earth, they do) but the outputted image > is just > a transparent square. > > Thanks > David > > > > On Mon, Feb 14, 2011 at 9:09 PM, Dane Springmeyer <[email protected]> wrote: > David, > > If you do not provide an 'srs' value for a <Layer ..> in your Mapnik XML then > the srs will be inherited from the <Map ..> 'srs'. In your case your Map is > correctly in Spherical Mercator but your data looks to be in WGS84, or > EPSG:4326. So, try changing your layer entry to look like: > > <Layer name="plots" srs="+init=epsg:4326" status="on"> > > When I do this things appear correctly when overlaid on top of OSM tiles > (when rendered with TileLite). > > It appears like your data is at: > http://tile.openstreetmap.org/17/21050/50798.png > > Dane > > > On Feb 14, 2011, at 3:22 PM, David Wiesen wrote: > >> When you say generate_tiles.py, do you mean this? >> >> http://svn.openstreetmap.org/applications/rendering/mapnik/generate_tiles.py >> >> When I generate the tiles myself, the lat/long calculations are correct >> (well, >> they match what I see here >> http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/) >> >> but it appears that the actual shapes from the shapefile don't match up with >> the base map >> provided by Google once the shapes are projected onto the png file. >> >> Thanks, >> David >> >> On Mon, Feb 14, 2011 at 3:15 PM, M∡rtin Koppenhoefer >> <[email protected]> wrote: >> I suggest you use generate_tiles.py and modify it. It will create >> tiles at the same position and zoom levels then google maps. >> >> cheers, >> Martin >> >> _______________________________________________ >> Mapnik-users mailing list >> [email protected] >> https://lists.berlios.de/mailman/listinfo/mapnik-users > >
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