[MetaCRS] Re: Google Spherical Mercator (EPSG:3785)

[Mikael Rittri]

Hello, 
I am new on this list.  Although Carmenta does not produce open source code,
I hope that I can contribute in other ways. 

About the Google Spherical Mercator, EPSG:3785 (discussed here in August 2008),
I would like to express my opinion that the EPSG choice of a spherical datum 
is confusing, counter-productive, and just plain unnecessary.  I would prefer 
a design where the datum simply is WGS84 (and I think it _is_ WGS84).  

Personally, I would prefer if WKT could express a design similar to the second one
mentioned by Melita Kennedy, where a parameter containing an integer (or an enumeration 
value) tells the Mercator how it should extract a spherical radius from the ellipsoid 
dimensions.  

On the other other hand, I can see the benefit of using existing WKT syntax 
with new meaning; that is, "semi_major" and "semi_minor" as Projection parameters,
as Martin Desruisseaux suggested.  I didn't know these were standard WKT, though.
Does OGRSpatialReference support them?  

There is an interesting poster on this subject by Terry Haran, National Snow and Ice Data Center, USA: 
ftp://sidads.colorado.edu/pub/ppp/conf_ppp/Haran/HDF-EOS_vs._GeoTIFF__GIS_Problems_when_Projection_and_Datum_Spheroids_are_Different.pdf

Best regards,

--
Mikael Rittri
Carmenta AB
Box 11354
SE-404 28 Göteborg
Visitors: Sankt Eriksgatan 5
SWEDEN
Tel: +46-31-775 57 37
Mob: +46-703-60 34 07 
mikael.rittri at carmenta.com
www.carmenta.com