[OpenLayers-Dev] [OpenLayers-Users] spherical-mercator

Christopher Schmidt crschmidt at metacarta.com
Wed Oct 3 00:50:23 EDT 2007

On Tue, Oct 02, 2007 at 11:16:36PM -0500, Lance Dyas wrote:
> Christopher Schmidt wrote:
> > * Use a WMS Server which support EPSG:900913 and sphericalMercator
> >   on the base layer.
> I keep meaning to ask this Why 900913
> I had previously seen 54004 and 41001

54004 and 41001 have both been used to describe the same thing -- that
is, the proj4 projection +proj=merc. Although this works well to a
point, it has issues in matching up exactly -- a more exact proj4 string
was uncovered by FrankW, as documented in
http://proj.maptools.org/faq.html#sphere_as_wgs84 .

Since the two things which are commonly used were already taken -- and
the former was really reserved for a different purpose anyway -- we went
with Tim's cute play on 'g o o g l e' -- 9 0 0 9 1 3. Can't tell me
you'll forget that now.

Christopher Schmidt

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