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Re: netCDF files and data access

>From: Lihua Li <address@hidden>
>Organization: University of Massachussetts
>Keywords: 199408222035.AA12492 netcdf

Lihua,

>       I'd like to open some netCDF files and access data from them,but I 
>have no idea about how to do that. Would you please introduce me some
>helpful materials and sample programs and tell me where I can obtain them.
>Thank you very much!


netCDF is a file format for holding data in a platform independant manner.
I have appended the netCDF README file for your information. There are
some sample files available on anonymous ftp to unidata.ucar.edu
in the pub/netcdf/sample_data directory. Theses files are binary in
nature, so remember to set your ftp transfer to binary mode.

In order to look at these files (that are binary in nature), you need to
create software to look at them. We provide a "library" that can be built
on a number of platforms that allow you to create programs that will be
able to read netCDF files. The UNIX version of the distribution (on our
ftp area) has a utility called "ncdump" that allows you to view the contents
of a netCDF file in ascii form. 

I suggest you look over the readme, then look around our ftp area for 
netcdf. You could then down load netcdf (netcdf.tar.Z), uncompress and
untar it, then build it on a system there. We use the netCDF format to
hold various weather and related data.

Mike Wright


                               Unidata netCDF
                               Version 2.3.2
                                 June 1993

The Unidata network Common Data Form (netCDF) is an interface for scientific
data access and a freely-distributed software library that provides an
implementation of the interface.  The netCDF library also defines a
machine-independent format for representing scientific data.  Together, the
interface, library, and format support the creation, access, and sharing of
scientific data.  The current netCDF software provides common C and FORTRAN
interfaces for applications and data.  It has been tested on various common
platforms, including several versions of UNIX, VMS, MSDOS, and OS/2.

NetCDF files are self-describing, network-transparent, directly accessible,
and extendible.  `Self-describing' means that a netCDF file includes
information about the data it contains.  `Network-transparent' means that a
netCDF file is represented in a form that can be accessed by computers with
different ways of storing integers, characters, and floating-point numbers.
`Direct-access' means that a small subset of a large dataset may be accessed
efficiently, without first reading through all the preceding data.
`Extendible' means that data can be appended to a netCDF dataset without
copying it or redefining its structure.

NetCDF is useful for supporting access to diverse kinds of scientific
data in heterogeneous networking environments and for writing application
software that does not depend on application-specific formats.  A variety
of analysis and display packages have been developed to analyze and
display data in netCDF form.

You can obtain a copy of the latest version of netCDF software using
anonymous FTP from

        host: unidata.ucar.edu
        file: pub/netcdf/netcdf.tar.Z

Included in this distribution are: the C source for the netCDF data
access library, sources for the FORTRAN jacket library for various
systems, documentation for the netCDF library and utilities in the form
of a netCDF User's Guide, source for the netCDF utilities ncdump and
ncgen, a directory of test programs to verify the correct implementation
of the netCDF library in new environments, and a directory of XDR
(eXternal Data Representation) source code for environments that do not
support XDR.

Other files available for anonymous FTP from the pub/netcdf/ directory of
unidata.ucar.edu include

 README                 general information about netCDF

 FAQ                    Frequently Asked Questions (with answers) about
                        netCDF.

 utilities.txt          a list of software packages currently available or
                        under development for manipulating and displaying
                        netCDF data

 guide.ps.Z             a compressed PostScript file of the NetCDF User's
                        Guide.  This is included in the netcdf.tar.Z
                        distribution, so you don't need both.

 ncprogs.ps             a draft PostScript document describing an initial
                        set of netCDF operator and utility programs under
                        development
                        
 ncprogs.txt            an ASCII version of ncprogs.ps

 conventions.info       a draft document of some proposed netCDF conventions

 cdl/                   a directory containing some examples of CDL files
                        (an ASCII representation for netCDF files).

 msdos/                 a directory containing executables and binaries for
                        netCDF under MSDOS 5.0.  These can also be built
                        from the sources in netcdf.tar.Z, if you have the
                        necessary Microsoft compilers.

 mac/                   a directory containing notes and Macintosh MPW
                        makefiles for porting netCDF to an Apple Macintosh.
                        These were contributed by Chuck Denham, U.S.
                        Geological Survey.

A mailing list, address@hidden, exists for discussion of
the netCDF interface and announcements about netCDF bugs, fixes, and
enhancements.  To subscribe, send a request to

        address@hidden

An archive of past postings to the netcdfgroup mailing list is available
for anonymous FTP from the file mail-archives/netcdfgroup of
unidata.ucar.edu.

A recent paper that provides a good introduction to the use of netCDF
appeared in

  Jenter, H. L. and R. P. Signell, 1992. "NetCDF: A Freely-Available
  Software-Solution to Data-Access Problems for Numerical Modelers".
  Proceedings of the American Society of Civil Engineers Conference on
  Estuarine and Coastal Modeling. Tampa, Florida.

This paper is available via anonymous FTP from

        host: crusty.er.usgs.gov
        file: pub/netcdf.asce.ps

Specific questions about netCDF that are not of interest to the
netcdfgroup mailing list may be sent to address@hidden.