So, OpenLayers wants to use a single well-known number to describe the ‘Google Projection’ I talked about earlier. 54004/54005/41001 are all ‘well known’ as being a standard Mercator projection. Which is not the Google Projection.
So, in addition to http://spatialreference.org/ref/user/google-projection/ / http://spatialreference.org/ref/user/6/ , we need something we can use in “SRS” in WMS — an EPSG code, such as it was.
In order to pick one that doesn’t conflict.
It’s the ‘Google’ projection — so we picked 900913. (Google. In 1337-speak.)
Use it. Love it. Promote it.
Comments
13 responses to “Google Projection: 900913”
Google in 1337 speak is 600613.
I think you should instead raise the concern with EPSG. The more people that pledge their case, the better chance there is that they will include it.
5VV337!
I don’t think it would be a bad thing to have a non-EPSG authority for some set of neo-geography SRS’s. On the other hand, since you do have to worry about a number collision, it may be time to have name spaces or even URI instead of numbers. I think EPSG:4326, or even 4326 are valid URI forms. So is http://spatialreference.org/ref/user/6
Hey Chris,
Quick question…
RE the post gis insert statement – why is the srid == 96?
I was expecting 900913.
Thanks
Paul
i think 900913 is great.
9-g
0-o
0-o
9-g
1-l
3-e
get it? 900913 is equal to google. THAT’S AMAZING ! =-)
EPSG has added a WGS 84 / Pseudo-Mercator Projection with a code of EPSG:3857 (See at http://www.epsg-registry.org/ )
They remark that “Uses spherical development of ellipsoidal coordinates. Relative to an ellipsoidal development errors of up to 800 metres in position and 0.7 percent in scale may arise. It is not a recognised geodetic system: see WGS 84 / World Mercator (CRS code 3395).”
EPSG had previously had this as a code of EPSG:3785 but this was deprecated under Change Request EPSG::2008.114 and so EPSG:3857 is now valid.
In addition, EPSG only use codes between 0 and 32767 (the equivalent of a positive signed short integer) any codes outside of this range are proprietary. Hence 900913!
http://spatialreference.org/ref/epsg/62556405/ is an EPSG code outside of that range. It is deprecated, but still in the distributed EPSG database.
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The value of the radius of the mean earth sphere in WGS84, which is used in EPSG: 3857, is not clear.
Is it the semi-Major-axis: 6.378.137 m?
Or is it the radius of the sherical approximation of the WGS84-ellipsoid: 6.371 km?
Bernhard Heckmann