[OSM-dev] Mercator projection

Christopher Schmidt crschmidt at metacarta.com
Sat Jan 13 02:14:32 GMT 2007

On Sat, Jan 13, 2007 at 03:07:59AM +0100, Kristian Thy wrote:
> Would it be correct to assume the Mercator projection being used for OSM
> is epsg:54004?

EPSG '54004' is not actually a definition. It is one of the codes in the
"user-defined" range allocated by the EPSG standards organization. I
assume you're using '54004' to describe the 'simple mercator' projection
used by Google. In that case, the projection for the WMS-C layer is 

The projection for the OSM tiles generated using generate_tiles.py is
not the same. It assumes a sphere, instead of an ellpisoid, for the
shape of the planet, so far as I can tell from reading the code, which
is what causes the difference in the two sets of tiles.

Christopher Schmidt

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