[GRASS-user] datum vs. sphere (grib files)

[Margherita Di Leo]

Hi,

I am currently using some grib files for meteorological data. When I set a
location referring to a "georeferenced grib file", a default WGS84 is
assigned to it, because datum is "unknown"

datum:      ** unknown (default: WGS84) **

Actually, the grib files are referred to a sphere, so that there is an
error related to the use of WGS84. Usually the resolution of grib data is
so coarse that it doesn't really affect the information, but now I need to
estimate correctly the error in a given point. To do that, I need to define
in GRASS a location using the "sphere" instead of the default WGS84. How
can I do that? Is there in PROJ4 the definition of "sphere", and a related
EPSG? why is it unknown?

Thanks for any hint.

Regards,

-- 
Dr. Margherita Di Leo
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