GMT is a free, open source collection of ~60 UNIX tools that allow users to
manipulate (x,y) and (x,y,z) data sets (including filtering, trend fitting,
gridding, projecting, etc.) and produce Encapsulated PostScript File (EPS)
illustrations ranging from simple x-y plots through contour maps to
artificially illuminated surfaces and 3-D perspective views in black and white,
gray tone, hachure patterns, and 24-bit color. GMT supports 25 common map
projections plus linear, log, and power scaling, and comes with support data
such as coastlines, rivers, and political boundaries.

GMT is developed and maintained by Paul Wessel and Walter H. F. Smith.

GMT is partly supported by the National Science Foundation.