On Fri, Feb 07, 2003 at 11:31:01AM -0700, John Caron wrote:
> Heiko Klein wrote:
>
> > Dear John,
> >
> > at the norwegian meteorological institute, we think about changing our
> > internal datatype to netCDF. I have seen the GDV convention and the
> > description seems to fit our data-needs, in particular, because it
> > offers the possibility to save data in stereographic projection.
> >
> > What I do not understand is how the coordinate axes have to be
> > implemented for stereographic projections. How can I give x and y km
> > units, when the distance of x1 and x2 depends on the y-value?
> >
> > It would be easier for me to understand the concept, if you could give
> > me the possibility to download some example files of the GDV convention.
> >
> > I tried to download some files from the IDV-program, but recognized,
> > that IDV-files (from motherload) don't use a convention at all.
> >
> > I hope you can help me further, or you may send this email further to
> > people who might help me.
> >
> >
> > Best regards,
> >
> > Heiko
> >
> >
> Hi Heiko:
>
> We are not currently recommending GDV Conventions, because we hope that
> the CF Conventions become widely adopted, especially for model data.
> They are in the process of adding support for data projections;
> hopefully that will be finalized soon.
>
> http://www.cgd.ucar.edu/cms/eaton/cf-metadata/index.html
>
> With regard to " x and y km units, when the distance of x1 and x2
> depends on the y-value". Typically the x and y are independent when they
> are expressed in units of "km on the projection plane". The lat and lon
> are then functions of both x and y, eg lat(x, y) and lon(x,y). I will
> see what examples I can find.
>
> I am forwarding this message to the CF discussion group, perhaps someone
> has an example of this in CF?
>
Hi John,
>From the User's Manual for the "proj" software I find:
The units of cartesian data are determined by the units used to define
the Earth's radius or ellipsoidal axes which are typically in meters.
FYI, the proj software is now being maintained at
http://www.remotesensing.org/proj.
Brian
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Brian Eaton | email: eaton at ucar.edu
Climate Modeling Section |
National Center for Atmospheric Research |
P.O. Box 3000, Boulder, CO 80307 |
Received on Sat Feb 08 2003 - 18:10:30 GMT
