GrADS Data Server (GDS)

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The GrADS Data Server

What is the GrADS Data Server?
The GrADS Data Server (GDS, formerly known as GrADS-DODS Server) is a stable, secure data server that provides subsetting and analysis services across the internet. The core of the GDS is OPeNDAP (also known as DODS), a software framework used for data networking that makes local data accessible to remote locations. GDS services can be provided for any GrADS-readable dataset: GRIB, Binary, NetCDF, HDF, BUFR, and GrADS station data format. The GDS unifies all these data formats into a NetCDF framework. The GDS subsetting capability allows users to retrieve a specified temporal and/or spatial subdomain from a large dataset, eliminating the need to download everything simply to access a small relevant portion of a dataset. The GDS analysis capability allows users to retrieve the results of an operation applied to one or more datasets on the server. Examples of analysis operations include basic math functions, averages, smoothing, differencing, correlation, and regression; the GDS supports any operation that can be expressed in a single GrADS expression. The GDS is based on Anagram, a modular framework for high-performace scientific data servers. For more information, please see the Anagram home page.

What do I need to install and run a GrADS Data Server?
The GrADS Data Server can run on any UNIX platform for which both Java and GrADS are available.

  • You need a Java Virtual Machine (JVM). Enter java -version at the Unix command prompt to find out what JVM you have currently installed on your system. The Java Virtual Machine is a free download either from Sun Microsystems, or your operating system manufacturer's website.
  • You also need GrADS. GrADS builds are available from the GrADS downloads page. GrADS and GDS are developed in synch: new versions of the server exploit new features in GrADS.
  • The newest release is GDS 2.0. This release was compiled with java 1.5 and requires GrADS 2.0.a2 or later.
  • The previous release is GDS 1.3. This release requires java 1.3 and GrADS version 1.9b4.

What's new in the latest version of GDS?

Important Note for GDS Administrators (June 2009): A recent release of GrADS (version 2.0.a6) implemented some necessary changes related to the handling of undefined values. These changes can affect the GDS. If you are administering a GDS version 2.0 with GrADS 2.0.a6 or higher behind it, then a 1-line patch is needed for the file $GDSHOME/scripts/ The patched version is here. Updating the script does not require a reinstallation or even a reload of your GDS.

GDS 2.0 has been upgraded for compatibiity with GrADS version 2.0. It handles data in GRIB2 format, and supports 5-Dimensional ensemble data sets. The server-side analysis capability is more flexible, so the result can vary in all 5 dimensions. See the README file for additional details.

GDS version 1.3 is now under the GNU public license -- please read the new COPYRIGHT. The java DAP class library has been upgraded to version 1.1.7 which implements DAP 2.0. The THREDDS catalog defaults to version 1.0. GDS version 1.3 also features a complete overhaul of attribute handling, with additional metadata for gridded and station data sets. The organization of environment variables and code relating to disk paths has been updated to support various server resources.

GDS version 1.2.9 added a new XML-based THREDDS catalog and support for high-resolution (<= 5km) and large (> 2Gb) data sets.

GDS version 1.2 and higher does not support the configuration file format used by GDS 1.1. You can upgrade easily by using this Perl script to automatically do the conversion: [FTP].

Where is the documentation?
The GDS documentation includes the User's Guide, the Administrator's Guide, the Configuration Reference Page, and the Source Code Documentation.

A list of some GDS sites:

COLA Climate Modeling Data Sets
COLA Weather and Climate Data Sets
National Centers for Environmental Prediction (NCEP)
NOAA Geophysical Fluid Dynamics Laboratory (GFDL)
NASA Goddard Space Flight Center (GSFC)
NOAA National Climatic Data Center (NCDC)
US Global Ocean Data Assimilation Experiment (GODAE)
Asia-Pacific Data-Research Center (APDRC/IPRC/SOEST)
GMU's Center for Earth Observing and Space Research
NOAA Forecast Systems Laboratory (FSL)
French Research Institute for Exploitation of the Sea (IFREMER)
International Centre for Theoretical Physics (ICTP)
Seoul National University (SNU)
Institute of Atmospheric Physics (IAP)
European Climate Assessment (ECA)

Reporting GDS problems and comments
You can report problems/feedback on the GDS three ways:
1. Post a message to the gradsusr mailing list
2. Send an email to: jma at cola dot iges dot org

Read more about the GDS
2001 AMS conference proceedings paper entitled "GrADS and DODS" by Joe Wielgosz and Brian Doty.
2003 AMS conference proceedings paper entitled "The GrADS-DODS Server: An open source tool for distributed data access and analysis" by Joe Wielgosz, Brian Doty, and Jennifer Adams.

GDS Support
Funding for GDS development and maintenance was provided by the SIESIP grant from NASA's Earth Science Information Partnerships.