GMT is an open source collection of ~60 tools for manipulating geographic and Cartesian data sets (including filtering, trend fitting, gridding, projecting, etc.) and producing Encapsulated PostScript File (EPS) illustrations ranging from simple x-y plots via contour maps to artificially illuminated surfaces and 3-D perspective views. GMT supports ~30 map projections and transformations and comes with support data such as GSHHS coastlines, rivers, and political boundaries. GMT is developed and maintained by Paul Wessel and Walter H. F. Smith with help from a global set of volunteers, and is supported by the National Science Foundation. It is released under the GNU General Public License.

Current version is 4.3.1, Released May 15, 2008.

GMT is used all over the world. Each yellow dot represent a 15x15 arc minute block with one or more registered user or institution. So far, over 1500 such blocks have been registered, representing more than 15,000 individual GMT users. To add your dot, fill out the registration form.