Re: netcdf4 and ncdump

Hello

On Fri, Jun 08, 2007 at 08:31:28AM -0600, Ed Hartnett wrote:
> Karsten Bolding <karsten@xxxxxxxxxxxxxxxxxxxx> writes:
> 
> > Hello
> >

<snip>

> 
> Feature or bug? Just a matter of definition, right? ;-)
> 
> This one is a bug. I see now what the problem is, and it will affect
> any variable in a group where the unlimited dimension is not defined
> in the same group. In this case, ncdump will treat the variable as if
> it were empty. 

OK 

<snip>

> 
> > Another question - I'm I right in the assumption that I can inherit
> > dimensions from the root group - as shown above - does that imply I also
> > inherit the root coordinate variables?
> 
> No it does not!
> 
> Coordinate variables are like any other variables. They are local to
> their group, and their varid is local to their group too. You need the
> varid and the ncid (which identifies both file and group) to identify
> a variable.
> 

That is a pity. I do not know anything about HDF and as such do not know
if it is because of HDF that the conventions used in NetCDF3 where a
variable with the same name as a dimension is a coordinate variable (or
maybe that is only in COARDS).

What I really like about NetCDF4 is the abillity to have multiple
unlimited dimensions (in my case it will always be time) since I'll use
it for storing regions (hyperslabs) in higher temporal resolution than
the rest of the domain. Often these hyperslabs will share one or more
dimension with the root dimensions e.g. root dimensions are e.g. (z,lat,lon)
and surface layer group is (time,1,lat,lon). Here I would find it
natural to be able also to re-use the coordiantes associated with
lat,lon. 
A frequent use of the multiple un-limited dimensions will be storing
high frequency data for positions corresponding to tide-gauge stations 
and buoys - could easy be more than 50 for the North Sea/Baltic Sea setup 
I mainly work with. Having 50 times the same vertical coodinate variable
in the same file is not very elegant.


Karsten


-- 
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Karsten Bolding                    Bolding & Burchard Hydrodynamics
Strandgyden 25                     Phone: +45 64422058
DK-5466 Asperup                    Fax:   +45 64422068
Denmark                            Email: karsten@xxxxxxxxxxxxxxxxxxxx

http://www.findvej.dk/Strandgyden25,5466,11,3
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