The Grid Analysis and Display System 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. 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. It uses the ctl mechanism to join differing time group data sets. 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 bargraphs, 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 that allows for sophisticated analysis and display applications. Scripts can display buttons and drop menus as well as graphics, and then take action based on user point-and-clicks. GrADS can be run inbatch mode, and the scripting language facilitates using GrADS to do long overnight batch jobs. As of version 2.2.0, graphics display and printing are now handled as independent plug-ins. A C-language Python extension for GrADS called GradsPy was introduced in version 2.2.1.
