Output in EPSG 3857 / ESRI 102100

Jun 15, 2010 at 4:44 PM
I'm trying to transform WGS84 coordinates to EPSG 3857 (ESRI 102100) coordinates. I have specified the WKT for the output coordinate system with this (and several variant) WKT: http://spatialreference.org/ref/sr-org/6928/. In every case the y-coordinates of my output are about 20km too small (only tested in SoCal). What do I need to do to correct this? -Dan Walton
Coordinator
Jun 16, 2010 at 5:32 AM

You can find the correct WKT in the WIKI: http://projnet.codeplex.com/wikipage?title=CommonWellKnownText&referringTitle=Home

Jun 16, 2010 at 5:56 AM

I am using that WKT, and for whatever reason it isn't properly overlaying a 102100 map service.

Jan 24, 2011 at 12:23 AM

Sounds like you might be creating a Mercator projection with respect to the WGS84 ellipsoid, rather than relative to a sphere. Try adding:

PARAMETER["semi_minor",6378137]

into the list of parameters in the WKT of your projection.

See here for more details: http://alastaira.wordpress.com/2011/01/23/the-google-maps-bing-maps-spherical-mercator-projection/