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Grid Analysis and Display System |
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The GrADS Data Server (GDS)
The GrADS Data Server (GDS), is a stable, secure data server that provides subsetting and analysis services across the internet. The core of the GDS is OPeNDAP, 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.
Required software to run a GDS
The GrADS Data Server can run on UNIX platforms for which both Java and GrADS are available. The three basic components are:
- Java Virtual Machine (JVM)
Enter"java -version"at the command prompt to find out what JVM you have currently installed on your system. The Java Virtual Machine is a free download either from Oracle, or your operating system manufacturer′s website. - GrADS
Builds are available from the GrADS downloads page. GrADS and GDS are developed in sync: new versions of the server exploit new features in GrADS. - GDS
The current GDS release is GDS2.0. This release was compiled with java 1.5 and requires GrADS 2.0.a2 or later.
GDS Documentation
The GDS documentation includes the User's Guide, the Administrator's Guide, the Configuration Reference Page, and the Source Code Documentation.
Release Notes
The steady stream of new GrADS releases give the GDS the capability to handle new data formats and products: HDF5 and NetCDF4, plus several new GRIB2 products, including Probabilities, Percentiles, Aerosols, and Ensemble Reforecasts (Product Definition Templates 5, 6, 9, 10, 48, 60, and 61). Support for large (>2GB) data files and new analysis functions in GrADS also enhance the server-side analysis capabilities of the GDS.
The 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/subset.gs. The patched version
is here. Updating the
subset.gs 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 1.3 was released 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: ini2xml.pl.
A list of some GDS sites
| INSTITUTION | GDS URL |
| COLA Weather and Climate Data Sets | http://monsoondata.org:9090/dods |
| National Centers for Environmental Prediction (NCEP) | http://nomads.ncep.noaa.gov/dods |
| NOAA Geophysical Fluid Dynamics Laboratory (GFDL) | http://nomads.gfdl.noaa.gov:9090 |
| NASA Goddard Space Flight Center (GSFC) | http://agdisc.gsfc.nasa.gov/dods http://nsipp.gsfc.nasa.gov:9090/dods http://voda.gsfc.nasa.gov:9090/dods http://goldsmr1.sci.gsfc.nasa.gov/dods http://goldsmr2.sci.gsfc.nasa.gov/dods http://goldsmr3.sci.gsfc.nasa.gov/dods |
| NOAA National Climatic Data Center (NCDC) | http://nomads.ncdc.noaa.gov/dods |
| US Global Ocean Data Assimilation Experiment (GODAE) | http://www.usgodae.org/dods/GDS |
| Asia-Pacific Data-Research Center (APDRC/IPRC/SOEST) | http://apdrc.soest.hawaii.edu/dods/ |
| GMU′s Center for Earth Observing and Space Research | http://spring.scs.gmu.edu:9080/dods |
| NOAA Forecast Systems Laboratory (FSL) | http://nomads.fsl.noaa.gov:9090/dods |
| French Research Institute for Exploitation of the Sea (IFREMER) | http://www.ifremer.fr/dodsG/ |
| International Centre for Theoretical Physics (ICTP) | http://clima-dods.ictp.trieste.it:9090/dods |
| Seoul National University (SNU) | http://cgcm.snu.ac.kr:9090/dods/ |
| Institute of Atmospheric Physics (IAP) | http://support.iap.ac.cn:7070/dods/ |
| European Climate Assessment (ECA) | http://eca.knmi.nl/dods/ |
Reporting GDS problems and comments
You can report problems/feedback on the GDS two ways:
1. Post a message to the gradsusr forum
2. Send an email to: jadams21 at gmu dot edu
Read more about the GDS
2001 AMS conference proceedings paper: GrADS and DODS
2003 AMS conference proceedings paper: The GrADS-DODS Server: An open source tool for distributed data access and analysis
GDS Support
Funding for GDS development and maintenance was initially provided by the SIESIP grant from NASA's Earth Science Information Partnerships. Current funding levels are adequate for user support and maintenance of the existing code.