Thank you much. I knew I was missing some key concept :) David
On Tue, Feb 15, 2011 at 9:51 AM, Dane Springmeyer <[email protected]> wrote: > 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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