[OSM-dev] Slippy map tiles mismatch

Matt Hampel matthew.hampel at gmail.com
Tue Feb 23 21:46:49 GMT 2010


On Tue, Feb 23, 2010 at 2:18 PM, Jon Burgess <jburgess777 at googlemail.com> wrote:
> On Tue, 2010-02-23 at 11:31 -0500, Matt Hampel wrote:
>> That's certainly possible, but I'm still not sure how to get closer to
>> a solution for pre-rendered tiles. To render the tiles, I'm following
>> steps at
>> http://wiki.openstreetmap.org/wiki/Slippy_Map and
>> http://wiki.openstreetmap.org/wiki/Mapnik#Rendering_tiles
>> using a shapefile extract instead of the full OSM export in PostGIS
>
> It should not make any difference whether you go down the pre-render
> route or not.
>
> What projection do you have in the <Map> element of your style?
>
> What does the definition of the shapefile datasource look like?
>

I have tried using two shapefiles (one reprojected into NAD83) and two
corresponding projections in the Map element.

NAD83:
<Map srs="+proj=latlong +ellps=NAD83 +datum=NAD83 +no_defs">

Layer SRS WKT:
GEOGCS["GCS_North_American_1983",
    DATUM["North_American_Datum_1983",
        SPHEROID["GRS_1980",6378137.0,298.257222101]],
    PRIMEM["Greenwich",0.0],
    UNIT["Degree",0.0174532925199433]]

--

<Map srs="+proj=latlong +ellps=WGS84 +datum=WGS84 +no_defs">

WGS84:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        TOWGS84[0,0,0,0,0,0,0],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.01745329251994328,
        AUTHORITY["EPSG","9122"]],
    AUTHORITY["EPSG","4326"]]




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