GRid Analysis and Display System

Overview Software Documentation Users Group List Server Forecast Data

Overview of GrADS

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 been implemented worldwide on a variety of commonly used operating systems and is freely distributed over the Internet (see the section below on downloading software).

GrADS uses a 4-Dimensional data environment, where the dimensions are longitude, latitude, vertical level, and time. Data sets are placed within this 4-Dimensional space by use of a data descriptor file. GrADS interprets station data as well as gridded data, and the grids may be regular, non-linearly spaced, gaussian, or of variable resolution. The format of the data represented by a descriptor file may be either binary, GRIB, or NetCDF. The 4-D data environment greatly facilitates intercomparison of disparate data sets. Operations may be performed between data on different grids, or between gridded and observational data. 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. The expression syntax allows complex operations to be performed with simple expressions. 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. A script may display widgets as well as graphics, and takes action based on user point-and-clicks. The scripting language can also be used to automate complex multi-step calculations or displays. GrADS can be run in batch mode, and the scripting language facilitates using GrADS to do long overnight batch jobs.

Downloading GrADS Software

GrADS is distributed free of charge, however certain copyright restrictions do apply. Versions of GrADS are available for several flavors of UNIX, Linux, PCs running Windows 95/NT or DOS, and MacIntosh computers. The sections below provide links to download the various versions of GrADS.

GrADS Executables for UNIX & Linux
UNIX and Linux versions of GrADS are available from COLA via anonymous ftp. These versions are distributed as several seperate tar files. The first tar file contains the binary executables for GrADS. Be sure to download the appropriate tar file for your particular hardware and operating system.

Operating System
GrADS v1.7 GrADS v1.8
DEC alpha.tar.Z Coming Soon
HP hpux.tar.Z Coming Soon
IBM aix.tar.Z Coming Soon
LINUX linux5.tar.Z Coming Soon
SGI irix5.tar.Z
Coming Soon
SUN sunos4.tar.Z

The executables contained in the first tar file are typically placed in the directory /usr/local/bin. If you do not have write permission for your /usr/local/bin directory, you can put them in the /bin subdirectory of your home directory.

After unpacking the tar file, you should have the following executables:

The second tar file contains the GrADS fonts and maps data sets. You can download it directly by clicking on the following link:


The contents of the data.tar are typically placed in the directory /usr/local/lib/grads. This is the GrADS default location for these files.

If you do not have write permission for /usr/local/lib/grads, you can place the files elsewhere, but you must also change the environment variable GADDIR so the GrADS executables will know where to find these files.

The third tar file contains a sample data set (gridded model output) along with a sample session to run through basic GrADS capabilities. If you have not used GrADS, you are strongly encouraged to obtain this file and go through the sample session. The file can be downloaded by clicking on the following link:


N.B.: If you are running GrADS on a DECstation and wish to run the example, you will need to first edit the data descriptor file (model.ctl) and remove the BYTESWAPPED record.

The contents of the tar files take about 5MB of disk space, depending on machine archetecture (64 bit executables are larger).

GrADS Executables for Windows 95/NT
The version of GrADS for PCs running Windows 95/NT is available HERE. To use this fully functional version of GrADS on the PC, you must have an X server running in order to display graphics. Complete details are provided at the link above.

GrADS Executables for DOS
The version of GrADS for PCs running DOS is available HERE. This is fully functional 32-bit version built with an X Windows emulation library under MS-DOS.

GrADS Executables for MacIntosh
A version of GrADS for the Apple Macintosh is available at The Mac version lacks some of the features of the Unix versions and is not actively maintained by COLA. See the README file for details.

An additional FTP site in Germany that provide GrADS executables is:

GrADS Metafile Viewer for Windows 95/NT
The GrADS metafile Viewer (GV) allows you to view and manipulate GrADS graphics output files using Windows 95/NT. There are two files to download:

To open the metafile simply double click on a file listed in the File Manager or Explorer, drag and drop the file onto GV, or use the standard Open dialog box. GV assumes that default extension of GRADS metafiles is GMF. If your file includes more than one picture you can browse through pages using the keyboard keys (PageDown and PageUp) or the toolbar buttons.

Use the View commands and the View/Options dialog box to customize the image -- display it as black-and-white or color, change the line thickness, or clip and enlarge any part of the image. Use the right mouse button to access the most commonly used features.

There are two ways to save separate pages of a GRADS metafile as Windows Metafile (WMF): 1) use the File/Save Page As command, or 2) use the Edit/Copy command to copy the current page to the Windows Clipboard and then Edit/Paste it in your favorite Windows application that handles Windows Metafiles.

Use File/Print command to print a current document to any printer (you do not need a Postscript printer). Use File/Print Preview to display the active metafile as it would appear when printed.

GrADS Documentation

The most up-to-date GrADS documentation is available online:

Hard-copy documentation is also available (but somewhat less current) in the following formats:

Additional information:

GrADS Users Group List Server

The list server is used for the exchange of information on GrADS: problem solving, script refinements, user defined functions, etc. Messages typically contain requests for help and ideas for solutions from users who have faced similar problems. Reference is frequently made to upgrades to GrADS and how to obtain them. All posts to the listserver are automatically despatched to all subscribed users, except the author. You will not receive a copy of your own posts.

In order to keep out spammers and internet marketers, subscription is no longer automatic. Send an email to the address below giving your affiliation, electronic and postal addresses, phone, etc. and you will be added by the system administrator.

To join, send email to:

Once subscribed, carefully read and archive the important information regarding the use of the listserver and how to send messages. Before posting to the listserver, check the online archive to see if your question has already been answered.

Last update: January 2001
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Center for Ocean-Land-Atmosphere Studies
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