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Re: 20050308: comments about netCDF web documentation

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  • Subject: Re: 20050308: comments about netCDF web documentation
  • Date: Tue, 08 Mar 2005 17:01:33 -0700
>Institution: Virginia Tech
>Package Version: Digital Visual Fortran (now Compaq) 6.6
>Operating System: Windows XP
>Hardware Information: No problems

Hi David,

>Inquiry: I am new to this Unidata cocept.  I downloaded data (VMAP2 daily
>surface data from ORNL- i.e. sradTCLMxxD3i.nc) and a dll, but I was under the
>impression that I would be able to find some fortran code to read these data.
>Have I missed something?  Probably.

Although the netCDF Fortran Users Guide includes example code
fragments for every netCDF function call, complete self-contained
example programs are sometimes more useful.  A program general enough
to read an arbitrary netCDF file (any dimensions, variables, and
attributes) is relatively complex, so doesn't make a good example to
learn from.

There are some relatively good primers available such as "A first time
primer for reading netCDF files":

  http://www.nodc.noaa.gov/woce_V2/disk10/html/ncprimer.htm

I've just whipped up a small Fortran example for reading data from a
simple netCDF file that looks like this (using "CDL" to show the
names, types, and shapes of variables, their attributes, and values):

  http://www.unidata.ucar.edu/packages/netcdf/examples/read1.cdl

The Fortran-90 program looks like this:

  http://www.unidata.ucar.edu/packages/netcdf/examples/read1.f90

The corresponding netCDF file to read is:

  http://www.unidata.ucar.edu/packages/netcdf/examples/read1.nc

You can generate netCDF example programs that write files using the
"ncgen" utility and CDL files.  For example, invoking

  ncgen -f read1.cdl

will generate, on stdout, a Fortran-77 program that creates the
read1.nc file above.  Similarly, "ncgen -c" generates a C program and
"ncgen -b" generates a binary netCDF file corresponding to a specified
CDL file.

I hope this helps get you started.  It's my intention to eventually
make available complete examples for the netCDF interfaces for C, C++,
Java, Fortran-77, Fortran-90, Python, Ruby, Perl, to supplement the
documentation for all these interfaces, but not much is done yet.

--Russ

_____________________________________________________________________

Russ Rew                                         UCAR Unidata Program
address@hidden          http://www.unidata.ucar.edu/staff/russ