Grid Analysis and Display System
The Grid Analysis and Display System (GrADS) is an interactive desktop tool that is used for easy access, manipulation, and visualization of earth science data. GrADS has two data models for handling gridded and station data. GrADS supports many data file formats, including binary (stream or sequential), GRIB (version 1 and 2), NetCDF, HDF (version 4 and 5), and BUFR (for station data). GrADS has been implemented worldwide on a variety of commonly used operating systems and is freely distributed over the Internet.
GrADS uses a 5-Dimensional data environment: the four conventional dimensions (longitude, latitude, vertical level, and time) plus an optional 5th dimension for grids that is generally implemented but designed to be used for ensembles. Data sets are placed within the 5-D space by use of a data descriptor file. GrADS handles grids that are regular, non-linearly spaced, gaussian, or of variable resolution. Data from different data sets may be graphically overlaid, with correct spatial and time registration. Operations are executed interactively by entering FORTRAN-like expressions at the command line. A rich set of built-in functions are provided, but users may also add their own functions as external routines written in any programming language.
Data may be displayed using a variety of graphical techniques: line and bar graphs, scatter plots, smoothed contours, shaded contours, streamlines, wind vectors, grid boxes, shaded grid boxes, and station model plots. Graphics may be output in PostScript or image formats. GrADS provides geophysically intuitive defaults, but the user has the option to control all aspects of graphics output.
GrADS has a programmable interface (scripting language) that allows for sophisticated analysis and display applications. Use scripts to display buttons and dropmenus as well as graphics, and then take action based on user point-and-clicks. GrADS can be run in batch mode, and the scripting language facilitates using GrADS to do long overnight batch jobs.
GrADS is now copyrighted under the terms of the GNU Public License; GrADS is distributed freely but without any warranty. See the COPYRIGHT file for more information. Versions of GrADS are available for several flavors of UNIX, PCs running MS Windows, and MacIntosh computers. The downloads page has instructions on obtaining the various versions of GrADS.
Online documentation has become the new standard for GrADS. The documentation page has links to the User′s Guide, a Tutorial, and a useful Index for quick reference. You can also get a tar file containing all the documentation web pages to install locally. Outdated hardcopy is also available.
A forum has been established for the exchange of information on the use of GrADS. Users at all levels are encouraged to post questions and answers on the basics of getting started, how to handle various data formats, where to find geophysical data sets in the public domain that are of interest to the GrADS community, discovering innovative solutions to data analaysis and display problems, script refinements, technical build issues, details about new releases, development requests, etc. Click on "GrADS Users Forum" link above for additional information.
The GrADS Data Server (GDS) is a stable, secure data server that uses the OPeNDAP protocol to provide subsetting and analysis services across the internet.
The following people have contributed to GrADS: Jennifer M. Adams, Reinhard Budich, Luigi Calori, Brian E. Doty, Wesley Ebisuzaki, Mike Fiorino, Tom Holt, Don Hooper, James L. Kinter, Steve Lord, Gary Love, Karin Meier, Matthias Munnich, Uwe Schulzweida, Arlindo da Silva, Michael Timlin, Pedro Tsai, Joe Wielgosz, Brian Wilkinson, and Katja Winger.
Support for GrADS development and maintenance comes from several sources. The original development of GrADS was funded by the NASA Advanced Information Systems Research Program. The development of the GrADS Data Server was funded by the SIESIP grant from NASA's Earth Science Information Partnerships. Ongoing support for GrADS is provided by an omnibus grant jointly funded by the NSF, NOAA and NASA that forms the core support for all research at COLA.