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# Preface to version 2.0 (Oct-1991)

When GMT was released at Lamont-Doherty Earth Observatory in the summer of 1988 it quickly became the standard data manipulation and plotting package which Lamont-Doherty scientists used to massage data and generate camera-ready maps and diagrams. Shortly afterwards color capabilities were added, and color maps and illustrations could easily be viewed under NeWS 1.3 on the SUN workstations, slides could be shot off the screen, and screendumps sent to various color hardcopy devices. Mostly by word of mouth, the number of GMT users among individuals and institutions elsewhere grew to include major research centers both in Europe and the U.S. The system proved easy to use, was general enough so that no matter what data you had, it could be manipulated and plotted, and it produced PostScript 1.4 output which could easily be edited to include custom enhancements. By keeping data files in the ASCII format, most trivial tasks of formatting and processing would be handled by UNIX utilities such as awk , grep , cut , paste , sed , etc.

GMT has undergone several modifications since its incarnation more than three years ago. The number of map projections available has doubled and now includes Mercator, Oblique Mercator, UTM, Stereographic, Lambert's conformal conic, Lambert's azimuthal equal-area, and Mollweide equal-area projections. In addition, non-map projections like log10(x) and xa have been added to the standard linear projection.

The plotting library pslib and the map drawing library gmtlib have been completely rewritten, resulting in higher quality graphics and more control over details. The PostScript macros defined in pslib have been optimized, resulting in smaller output files and shorter execution times.

A major new feature is the concept of the .gmtdefaults file. In this file, which will reside in the user's home directory, we find more than 50 parameters including the pen-thicknesses, font-types, and colors to use for maps, which ellipsoid to employ in the map projections, and what units to operate in (cm, inch, or meter). All of these can be set individually by the user, thus customizing GMT defaults to produce the desired results without excessive command line arguments when running individual programs or having to edit the PostScript files at a later stage.

In order to make the operation of GMT programs more efficient, the notion of a command history has been implemented. The history remembers the previous standardized command line arguments used with any GMT program and allows the user to use a shorthand when the same argument is needed. This information is stored in a file called .gmtcommands which is maintained in the current directory. Thus more than one .gmtcommands file can exist at the same time.

Finally, the format used for storing 2-D gridded data sets has been changed. The new format is based on the XDR architecture-independent data representation as implemented in the netCDF software package available from NCAR (See Appendix D for how to obtain the necessary code). The advantages of using this new format are many; here we will just mention scanline orientation and the ability to transfer your binary gridded data sets from one type of computer to another which may not have the same way of representing floating point numbers.

With all these enhancements, GMT now supports most accepted standards of today's computing environments: UNIX, PostScript, ASCII tables, and XDR binary file protocol. We hope the new version 2.0 of GMT will enhance your productivity and make data manipulation and presentation a little bit easier. Should you have any suggestions to future enhancements and modification, we would like to hear from you. Please send your comments to gmt@soest.hawaii.edu.

Next: Introduction Up: Prefaces Previous: Preface to version 2.1