GMT was created in 1988 by Paul Wessel and Walter H. F. Smith, and has undergone several revisions and major enhancements since then. The current version is 4.3.0. GMT is supported by the National Science Foundation.

As of May 2008 it appears that over 15,000 scientists and engineers worldwide are using GMT in their work. This estimate is based on ftp traffic and returned registration forms over the last few years. Most users of GMT are Earth scientists, but there are apparently no limits to the kind of applications that may benefit from GMT: We know GMT is used in medical research, engineering, physics, mathematics, social and biological sciences, and by geographers, fisheries institutes, oil companies, and a wide range of government agencies.

Yes. GMT is written in ANSI C and is POSIX and Y2K compliant. Furthermore, it can read time-series data that are "Y2K-challenged" (i.e., 2-digit years only).

GMT has been installed on a variety of UNIX systems, including (but not limited to) computers from Cray, Sun, IBM, DEC, HP, SGI, Data General, Apple (Mac OS X), and Next, all running some flavor of UNIX. GMT has also been installed under Linux and MkLinux, which are open source UNIX-like operating systems for PC and Mac OS 9, respectively. GMT also installs under all flavors of Windows and OS/2. GMT is very portable and should compile on almost any computer.

Yes. Many GMT users with PCs simply install Linux in addition to Windows and boot either operating system. If you do not have or want to install a UNIX operating system on your PC, there are two ways to go:

1. Run a UNIX environment on top of your other operating system. Under Windows you could install Windows Services for UNIX (formerly Interix and OpenNT), which gives you a free, POSIX-compliant environment with the usual UNIX tools (shells, awk, grep). Another no-cost option is to install the Cygwin package which also gives you a POSIX-compliant UNIX environment on your PC in which GMT may be installed. Under MacOS 9 or earlier you could install MachTen which does the same thing on an older Machintosh (Mac OS X, of course, is UNIX-based). We prefer the UNIX-options for Windows over DOS-style batch scripts since many tasks that GMT is used for depend strongly on access to UNIX tools such as csh, awk, grep, sed, etc.

2. Install GMT directly in Windows or OS/2. You could do this from scratch if you have a compiler (GMT comes with instructions for Microsoft Visual C/C++ compiler), or simply install the pre-compiled Win32 executables from the ftp sites. Sorry, there is no such option for MacOS 9 or earlier. If you have MacOS X you can install GMT as on any UNIX workstation.

Disk space: GMT contains some 100,000 lines of code. On a Linux workstation the executables take up about 15-50 Mb depending on use of shared libraries. In addition there are support data such as GSHHS coastlines, rivers, and political boundaries. The default distribution of these data includes intermediate, low and crude resolution versions which together takes up another 5 Mb of space. These are sufficient for most regional map applications. Optionally, the user may install the high and full resolution data sets, taking up additional 13 Mb and 60 Mb, respectively. Complete PS/HTML/MAN documentation adds another 40 Mb. Thus, a complete GMT installation may take up around 200 Mb.

Memory: All GMT modules use dynamic allocation of memory and may therefore run on systems with modest memory resources such as personal computers. However, some operations such as gridding and manipulation of large data sets will require more memory to run. GMT was written with the understanding that there would be enough memory to do a task without breaking it into smaller pieces. Increasing swap space may overcome some memory limitations.

Yes. Yes. GMT now supports full 64-bit addressing and has been tested under OS X. Our automated script, however, does not yet offer the option to compile in 64-bit. To test, pass the --enable-64 flag to configure; you may have to modify CFLAGS, LDFLAGS etc. manually unless you run OS X.

You need a C compiler to compile the package. Your system may already have one installed as cc; otherwise you can get the GNU gcc compiler for free by the good guys at GNU. GMT uses the netCDF library which you must install prior to installing GMT (the install script will do this for you).

No. As distributed, GMT is a command-line oriented package. This was a deliberate decision: A graphical user interface (GUI) would place limits on what can be done; in return it would make the system more user-friendly. We placed the premium on flexibility and performance; our experience has been that the command-line interface allows users to connect GMT modules to other custom programs and arrive at unique results. The combination of GMT and shell-scripting allows for very powerful programming and automation of repetitive tasks.

However, GMT can easily be called from within a GUI. Several packages by third-party developers provide GUI access to GMT:

• iGMT (interactive Mapping of Geoscientific Datasets) which is an interface built using the Tcl/Tk toolkit
• Win4GMT, a GUI for Windows 95/98/00/NT.

• Those who are using GIS, in particular Arc/INFO and ArcView, may be interested in arcGMT, a suite of tools for conversion between Arc/INFO and GMT.
• For multi-beam enthusiasts, there is MB-System, a software package for the processing and display of swath sonar data

• Lots of data from the US national data centers (NOAA, USGS, NGDC, NEIC) can be used with GMT, and they are all freely available from these centers and individuals via the internet. For Unix/OSX/Windows DVD-R compilations of several Gb of Earth and Ocean science data, see Geoware's GMT CompanionDVD-R products.

The best reference to GMT is an article by Wessel and Smith published in EOS, the transactions of the American Geophysical Union, on Oct 8th 1991 (Wessel, P. and W. H. F. Smith, Free software helps map and display data, EOS Trans. AGU, 72, 441, 1991).

We had a news release in EOS that discussed the 3.1 version (Wessel, P. and W. H. F. Smith, New, improved version of the Generic Mapping Tools released, EOS Trans. AGU, 79, 579, 1998). Furthermore, the electronic supplement for EOS contains a more detailed article describing the GMT 3.0 release.

The GMT distribution also contains an ~150-page Technical Reference and Cookbook with many examples of GMT usage, in addition to separate UNIX man pages for each program.

Another reference which documents one gridding algorithm used by GMT is an article by Smith and Wessel in Geophysics, vol. 55, pp. 293-305, 1990.