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

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GMT The Generic Mapping ToolsPaul 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 20052010.
• 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?