[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[netCDF #REI-388162]: extract of a data file

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: [netCDF #REI-388162]: extract of a data file
  • Date: Wed, 04 Jul 2012 17:59:53 -0600
Hi,

> I am looking for a way to extract a piece of netCDF data file, and
> then display it on a web map server using ncWMS. I am interested in the
> North shore of Australia, so I would like to download only this part of
> the globe.
> 
> Do you know how can I do it?

Yes, but it depends on how the data is represented.

First, the data must follow conventions for how it is mapped to location
on the globe, "geolocated" for short.  The CF Conventions for NetCDF
Metadata provide a standard for acceptable geolocation information.
If your data is "CF-compliant", then you can specify the subset you want
in terms of earth coordinates.

If the data is available from a server that supports WMS, for example a
Unidata THREDDS server, then you can just use the ncWMS web client to
display or access the data.  For more information and examples, see

  http://www.resc.rdg.ac.uk/trac/ncWMS/

Alternatively, the NetCDF Subset Service (NSS) for gridded data
supported experimentally in THREDDS provides another way to get data 
that's properly geolocated:

  
http://www.unidata.ucar.edu/projects/THREDDS/tech/interfaceSpec/GridDataSubsetService.html

If the data is only available as a local file rather than on a server,
you can still get a subset of the data by using software that
understands CF conventions and can extract the data.  For example:

  - NCO, which has a utility program, ncks, that can extract a subset of
     a lat-lon grid:
       http://nco.sourceforge.net/
  - NCL provides both subsetting and extensive display capabilities:
       http://www.ncl.ucar.edu/overview.shtml
  - CDO provides such subsetting for climate data, e.g. see SELBOX
     command:
       https://code.zmaw.de/embedded/cdo/1.5.5/cdo.html
  - Commercial packages provide software and systems for this kind of
    use, for example see some of the software described in the
    "Commercial or Licensed Packages" section here:
       http://www.unidata.ucar.edu/software/netcdf/software.html      

--Russ

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



Ticket Details
===================
Ticket ID: REI-388162
Department: Support netCDF
Priority: Normal
Status: Closed