Re: 950314: Question about netCDF

>Organization: .
>Keywords: 199503140527.AA11375

Hi Hirokazu,

>  I am currently conducting a survey about data formats that are currently
>  used for domestic and international scientific data exchange.
>  For this survey, I would like to collect some basic information about
>  netCDF such as ;
> 
>  1. Major users (organization)

To see some of the users for netCDF, you can use a WWW browser (such as
Netscape or Mosaic) to look at the netCDF homepage:

    http://www.unidata.ucar.edu/packages/netcdf/

where there are links to "Who uses netCDF?" and information about "Mailing
Lists".  If you don't have a WWW browser, you can get copies of text
versions of these files via anonymous FTP from:

    ftp://ftp.unidata.ucar.edu/pub/netcdf/usage.txt

and

    ftp://ftp.unidata.ucar.edu/pub/netcdf/mailing-lists.txt

If you have no access to text files via anonymous FTP, let us know and we
will email copies of the above documents.

To get a list of all the email addresses on the netCDF mailing lists, from
which you can get an idea of the organizations and countries where netCDF is
used, send an email message to address@hidden with a blank
subject and containing the following two lines as the message:

who netcdfgroup
who ncdigest

>  2. Major usage

I'm not sure what you're asking for here, but there is information about how
netCDF is used in the "usage" document referred to above.

>  3. Basic features

   netCDF data is:
     
   + Self-Describing: A netCDF file includes information about the
     data it contains.
     
   + Network-transparent. 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. A small subset of a large dataset may be
     accessed efficiently, without first reading through all the
     preceding data.
     
   + Appendable. Data can be appended to a netCDF dataset along
     one dimension without copying the dataset or redefining its
     structure. The structure of a netCDF dataset can be changed,
     though this sometimes causes the dataset to be copied.
     
   + Sharable. One writer and multiple readers may simultaneously
     access the same netCDF file.
   
>  4. Merits and demerits

To see a comparison with other scientific data access software, see the
article: 

       Brown, S. A, M. Folk, G. Goucher, and R. Rew, "Software for
       Portable Scientific Data Management," Computers in Physics,
       American Institute of Physics, Vol. 7, No. 3, May/June 1993, pp.
       304-308.

Also, there is some information comparing the various packages available in
the "Scientific Data Formats FAQ" document, viewable with a WWW browser from

    http://fits.cv.nrao.edu/traffic/scidataformats/faq.html

or in ASCII text form via anonymous FTP from 

    ftp://rtfm.mit.edu/pub/usenet/news.answers/sci-data-formats

The advantages and disadvantages of netCDF is a complex subject, since the
netCDF data model, interface, software, and format reflect subtle trade-offs
between usability, generality, understandability, maintainability, and
efficiency in size and CPU time.

For example, one advantage of netCDF is the unlimited dimension it provides,
which makes it possible to append data to existing netCDF datasets.  One of
the disadvantages of netCDF is that it has only one unlimited dimension per
dataset, but this limitation is intentional since it permits a
straightforward and efficient implementation.

There are dozens of other similar tradeoffs, and some are irrelevant for
many applications, while others may be of crucial importance in deciding
among available packages for a specific use.

______________________________________________________________________________

Russ Rew                                                UCAR Unidata Program
address@hidden                                          P.O. Box 3000
http://www.unidata.ucar.edu/                          Boulder, CO 80307-3000
______________________________________________________________________________