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. The format of the data may be either binary, GRIB, NetCDF, or
HDF-SDS (Scientific Data Sets). GrADS has been implemented worldwide on
a variety of commonly used operating systems and is freely distributed
over the Internet.
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GrADS uses a 4-Dimensional data environment: longitude, latitude,
vertical level, and time. Data sets are placed within the 4-D 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. 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.
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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.
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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.
