GMT: The Generic Mapping Tools

Paul Wessel, Walter H.F. Smithand the GMT team

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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 1993. 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

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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

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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

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GMT Software Requirements

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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

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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

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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

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GMT Symbols and Patterns

1. Standard Geometrical shapes

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GMT Symbols and Patterns

2. User-defined symbols

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GMT Symbols and Patterns

3. Faults, Fronts, and other demarcations

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GMT Symbols and Patterns

4. Pattern fill

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All GMT tools work together

The GMT Cake Bake

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Using the GMT Map Engine

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(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

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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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Questions?