The idea that coordinate specifications can be fully described by a code
which refers back to a remote repository of meta-data is very much the
same philosophy adopted years ago by the WMO's GRIB standard. When I
first encountered GRIB I was amazed and frightened. But more and more I
am hearing cyber-infrastructure gurus recommending the existence of
meta-data repositories for data discovery as well as data descriptions.
So I think it is a valid idea to assume the existence of such data
repositories. EPSG might be only one of many (including a NOAA CF
repository?). However I still do not like to have to rely upon them. I
hope that we can go down the middle, and allow the use of code names for
exotic transformations to the "Aztec Oblique Rhombodal Orthogonal" while
allowing simpler more common ones to include, as attributes, all the
metadata needed to decode.
Tom Gross
Chesapeake Community Model Program
ccmp.chesapeake.org
Chesapeake Research Consortium
Edgewater, MD 410-798-1283
or on Monday and Tuesdays
tom.gross at noaa.gov
NOAA/NOS/Coast Survey Development Lab.
Silver Spring, MD (301) 713-2809 x139
-----Original Message-----
From: John Caron <caron at unidata.ucar.edu>
Sent: Thursday, February 17, 2005 3:17 PM
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] Horizontal Data Coordinate System Definition
[long]
Richard P Signell wrote:
>John & Co,
>
>I think that requiring either ellipsoid paramaters OR EPSG code is a
good
>idea, but I'm not sure we should limit the EPSG codes people can use.
>While I agree it would be pretty unreasonable to expect clients to
support
>*all* EPSG codes, CF is already so complex that clients will probably
only
>implement selected features. The IDV is an example.
>
>
>If someone wants to write a client that will access the EPSG database
and
>implement every projection and transformation in, we shouldn't stop
them.
>And also it would be sad to tell people that their model using Swiss
>Oblique Cylindrical coordinates cannot be described with CF. ;-)
>
>-Rich
>
>
Hi Rich:
I would be ok allowing any EPSG codes, or listing the allowed ones.
Probably the CF principals should decide.
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Received on Thu Feb 17 2005 - 14:37:58 GMT
