GMT: The Generic Mapping Tools Paul Wessel, Walter H.F. Smith and the GMT team

GEON Workshop What is GMT? GMT stands for Generic Mapping Tools GMT is jointly developed by Paul Wessel (UH) and Walter H. F. Smith (NOAA), with voluntary community support from around the world GMT was initiated in 1987 and has been supported by NSF since GMT 5 funded for 2005–2010. GMT is used by 10,000+ users worldwide GMT is open-source and platform independent GMT does data processing and static visualization GMT consists of 60+ individual programs with several supplemental units

GEON Workshop The Origin of GMT Conceived in the pre-web era Intended for paper illustrations Influenced by late 1980ies trends UNIX-style “filters” written in POSIX C Standard file format in ASCII or netCDF Adobe PostScript as plot format Plain command-line interface Very flexible and integrates with shell tools Others may add GUIs, i.e. iGMT, or Web- portals

GEON Workshop Why is GMT popular? Price is right! Easy to install; runs on all platforms Architecture-independent file formats ASCII and netCDF Quality PostScript graphics Extensible via supplements Developers are scientists and users Low-tech with a wide range

GEON Workshop GMT Software Requirements

GEON Workshop What can GMT do? Data Processing and Manipulation Relies on UNIX tools for basic tasks PostScript Plot Generation Tools can convert PS to raster images GMT is neither a GIS nor an image processing package

GEON Workshop Data Processing & Manipulation Filter time series Filter 2-D data Trend fitting Gridding xyz data Resampling Arbitrary math ops Cut/paste grids Blend grids Directional derivatives Grid masking Data projections Optimal triangulations Subset extraction Spectral estimation RGB from z grids

GEON Workshop PostScript Plot Generation x-y diagrams of lines, polygons, symbols Plot text, labels, and map legends Rectangular or polar histograms Basemaps with coastlines, rivers, and borders Contour maps Color images Perspective views (2.5 D) with illumination Vector fields

GEON Workshop

10 GMT Symbols and Patterns 1. Standard Geometrical shapes

GEON Workshop GMT Symbols and Patterns 2. User-defined symbols

GEON Workshop GMT Symbols and Patterns 3. Faults, Fronts, and other demarcations

GEON Workshop GMT Symbols and Patterns 4. Pattern fill

GEON Workshop All GMT tools work together The GMT Cake Bake

GEON Workshop Using the GMT Map Engine

GEON Workshop (Some) GMT Shortcomings Lack of high-level API Too much of GMT functionality is encoded directly in the executables, necessitating system calls Legacy Problems 2-D grids stored as 1-D arrays in netCDF Geographical boundary conditions not implemented throughout Splines-in-tension gridding code needs to be transposed

GEON Workshop Anticipated GMT Improvements Design and implementation of GMT 5 API Callable high-level functions from C/C++, Fortran, Python, Visual Basic, Java, Perl, etc. Complete documentation of the GMT API Correction of legacy problems Introduction of new features True perspective view Generalized custom symbols with multiple attributes Easier data exchange with GIS Web-based GMT Map-maker

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