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GMT: The Generic Mapping ToolsPaul Wessel, Walter H.F. Smith

and the GMT team

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GEON Workshop 2005 2

What is GMT?

GMT stands for Generic Mapping Tools

GMT is jointly developed by Paul Wessel (UH) andWalter H. F. Smith (NOAA), with voluntarycommunity support from around the world

GMT was initiated in 1987 and has been supportedby 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 severalsupplemental 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 PostScriptas plot format

Plain command-line interfaceVery 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 formatsASCII and netCDF

Quality PostScriptgraphics

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

PostScriptPlot 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

Directionalderivatives

Grid masking

Data projections Optimal

triangulations

Subset extraction Spectral estimation

RGB from z grids

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PostScriptPlot Generation

x-ydiagrams 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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2. User-defined symbols

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3. Faults, Fronts, and other demarcations

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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 multipleattributes

Easier data exchange with GIS

Web-based GMT Map-maker

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Questions?

Documents

Gmt Geon2005