As of January 1995 it appears that around 5000 scientists and engineers worldwide are using GMT in their work. This estimate is based on ftp traffic over the last few years. Most users of GMT are geoscientists, 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.
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The present version 3.0 represents a significant improvement over
earlier releases. The most visible change is the inclusion of a
high-resolution coastline data base which will allow the generation
of small-scale, detailed maps of high quality and accuracy (see
Appendix K for more details). In addition, we have added three
more map projections, six new programs, modified and added new
options to others, and killed numerous bugs. The file CHANGES on
the tar archive has all the details; here are some highlights:
Customizable grdfile i/o.
This allows the user to supply his/her own read/write kernels, link these with GMT during installation, and be able to use GMT programs directly with the user’s data files. This mechanism also speeds up many operations by letting the user select a format that allows piping instead of saving the results of intermediate steps to temporary files (as is necessary with the netCDF format). In addition to the default netCDF-based gridfile format, GMT comes equipped with 3 additional formats:
The file gmt_customio.c contains information on
how to add more formats. We anticipate that formats of general
interest will be developed by enterprising users and forwarded
to us for possible inclusion in later GMT releases.
Binary i/o option for several i/o intensive programs.
Several programs typically read and/or write large amounts of
data These include blockmean , blockmedian ,
grd2xyz , nearneighbor , splitxyz , surface , and xyz2grd . These programs are
often used to decimate vast quantities of data, but much of the
processing time can be spent on the ASCII-binary conversion
during read and write. A new -b option allows these
programs to do their i/o in native binary format (single or
double precision).
4+ new map projections.
We have included the Robinson pseudo-cylindrical projection
(adopted by the National Geographic Society), the Eckert VI
equal area projection, the Plate Carrée equidistant
cylindrical projection, and a generic cylindrical equal area
projection. The latter accepts an arbitrary standard latitude:
Set to 0o, 30o, 37.4o, or 45o you obtain the Lambert,
Behrmann, Trystan-Edwards, and Peters (Gall) cylindrical
projections, respectively. Furthermore, we have generalized
the sinusoidal projection. The interrupted map on the cover
page is a superposition of three sinusoidal plots that are
offset horizontally.
6 new programs.
Programs have been added to address several important tasks:
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Simpler map projection option -–J*.
All projections may now be specified with upper or lower case modifier *: Lower case works as before (it expects map scale), while upper case expects map width. This makes it much easier to fit a plot on the page. E.g., -–Jm5 will generate a Mercator map in which 1o of longitude equals 5 inches (or cm, depending on your choice of units), while -JM5 will make a map that is 5 inches (or cm) wide regardless of region selected (in both cases, the height will of course depend on region).
All projections now accept arbitrary regions in the -–R
option (in earlier versions there were some projections that
implicitly assumed a global map -R0/360/-90/90).
Improved syntax checking.
All GMT programs now have extensive syntax checking and give
shorter and more meaningful error messages. It is only when
no arguments are provided that the entire usage message will
be echoed.
Better SI support
During installation of GMT you may choose to use SI units as
your default (basically, it means that plot sizes are measured
in cm instead of inch). This will modify the source code to
show the SI default values and produce man pages using SI units.
However, you can always override the defaults by modifying your
.gmtdefaults file.
Operational changes.
A few modifications of command arguments have taken place. If you have developed shell-scripts with GMT commands you may need to edit these accordingly:
Several programs have received additional options.
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The documentation (this book plus all manual pages) has been updated
to reflect these changes. Two new appendices (J, K) discussing the
finer points of filtering and the development of the high-resolution
coastline data base have been added.
Finally, we would like to thank those of you who have contributed ideas, bug reports, and advice since version 2.1. We continue to appreciate your input, and believe version 3.0 reflects many of the suggestions you have provided.