[Proj] Google Mercator Projection

zagot maurelio at live.it
Thu Aug 4 00:23:15 PDT 2011


Hi to All,
this is an oldie, but i cannot seem to find a solution.
When i want to do a transform on a wgs84 to google/bing the y coordinate
shifts.

I have read this  variuos post and this official note:
http://trac.osgeo.org/proj/wiki/FAQ#ChangingEllipsoidWhycantIconvertfromWGS84toGoogleEarthVirtualGlobeMercator

...so I tried adding +nadgrids=@null like i read, but with this example:

from ..."+proj=latlong +datum=WGS84";

to... "+proj=merc +a=6378137 +b=6378137 +lat_t1=0.0 +lon_0=0.0 +x_0=0.0
+y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs"

i have this result -626172.1357121646,  6887893.4928337997 

in the result y differ from correct value:6853955.508199729 (with Proj.NET
the result is correct)

..seems adding +nadgrids=@null  have no effect

what's I wrong?

thanks in advance

sorry for my english
thanks


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