John,
There are two "sphere" ellipsoids recognized by the EPSG:
Clarke 1866 Authalic Sphere (EPSG_code=7052); radius=6370997
GRS 1980 Authalic Sphere (EPSG_code=7048); radius=6371007
Both of these spheres were designed to have the volume of the sphere match the
true ellipsoid, and the slight difference of 10 meters represents the progress
in understanding the ellipsoid over the 114 years!
It sounds like you would like to use the older one, and since it hasn't been
specified, we assume it doesn't matter, but...
I would choose the GRS 1980 value, just to "sound" more modern (so that people
wouldn't ask me why my netcdf data was based on something that came from 1866)
-Rich
John Caron <caron at unidata.ucar.edu>
> So would everyone agree, that in the absence of explicit information, I
> could use, say, a spherical earth with radius 6370997 m as a reasonable
> default ?
>
>
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--
Richard P. Signell rsignell at usgs.gov
U.S. Geological Survey Phone: (508) 457-2229
384 Woods Hole Road Fax: (508) 457-2310
Woods Hole, MA 02543-1598
Received on Tue Apr 05 2005 - 10:10:49 BST
