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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.
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.
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.
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