GNU Data Language (GDL) - a free and open-source implementation of IDL Sylwester Arabas1, Marc Schellens*, Alain Coulais2, Joel Gales3, Peter Messmer4, and many other volunteers all around the world** *: Marc is the primary author and the maintainer of GDL **: a list of contributors is available at the project’s website (http://gnudatalanguage.sf.net/) and in the AUTHORS file of the GDL tarballs and packages 1: Institute of Geophysics, University of Warsaw, Poland; 2: LERMA, CNRS and Observatoire de Paris, Paris, France; 3: NASA Goddard Space Flight Center, Greenbelt, Maryland, USA; 4: Tech-X Corporation, Boulder, Colorado, USA About GDL Dependencies and useful libraries (all free & open) Example usage of GDL for classroom work on data analysis GNU Data Language (GDL) is developed with the aim of providing an open-source drop-in replacement for the ITTVIS’s Interactive Data GDL is an incremental compiler with integrated debugging facilities. It is written in C++ using the GDL proved to be a useful tool for classroom work on data Language (IDL). It is developed by an international team analysis. In 2010 it was used for the second time as a data-analysis of volunteers led by Marc Schellens - the project’s founder (a list ANTLR language-recognition framework. Extensions to GDL can be written in C++, GDL, and of contributors is available on the project’s website). GDL with its library Python. Most of the library routines are implemented as interfaces to open-source libraries: environment during a meteorological-data processing course routines is designed as a tool for numerical data analysis and Craig taught at the Institute of Geophysics, University of Warsaw. The visualisation. As its proprietary counterparts (IDL and PV-WAVE), . .g Markwardt's e GDL is used particularly in geosciences and astronomy. GDL is MPFIT course covers hands-on training in handling of scientific data sets. dynamically-typed, vectorized and has object-oriented programming curve fitting, function (IDL-written libraries minimi- GDL is used for reading GRIB, netCDF & HDF files, and capabilities. The library routines handle numerical calculations, data functional under GDL) zation UNIDATA's UDUNITS GNU performing basic data analysis and visualisation tasks. GDL compressing weather-radar images visualisation, signal/image processing, interaction with host OS and data Craig input/output. GDL supports several data formats such as netCDF, Markwardt's Scientific Library using truncated wavelet approximation. CMSVLIB HDF4, HDF5, GRIB, PNG, TIFF, DICOM, etc. Graphical output NASA's IDL's SAVE (GSL) is handled by X11, PostScript, SVG or z-buffer terminals, the last one files I/O Astron lib simple linear algebra, random allowing output to be saved in a variety of raster graphics formats. While incl. FITS IO MIT's numbers, histograms, interpolation, still being in its beta-stage of development (see Coulais et al., 2009), splines, root-finding, physical constants FFTW catalogue, wavelets, GDL proved to be a usable tool both for research (Jaffey et al., 2008, etc 2009) and teaching purposes (outlined hereby). GDL is released under UNIDATA's the GNU GPL licence - you are free to use it, to share it with anyone, netCDF to modify and improve it, and to share the modified version with anyone. HDFGroup's GDL plotting weather-forecast map from a GDL used for demonstrating Kalman Contributions and users’ feedback are welcome! HDF5 GRIB file with NOAA GFS model output. Gerald I. filtering on randomly-generated signal. References HDFGroup's Evenden's GDL used as a part of a web-interface for HDF4 C++ libproj4 controlling 2D fluid flow simulation and Coulais, A., M. Schellens, J. Gales, S. Arabas, M. Boquien, P. Chanial, P. Messmer, ECMWF's STL, GCC visualizing the output (reading netCDF files D. Fillmore, O. Poplawski, S. Maret, G. Marchal, N. Galmiche, and T. Mermet, 2009: GRIB API and outputting SVG plots). Status of GDL - GNU Data Language. Astronomical Data Analysis Software and Systems XIX , ASP Conference Series, Sapporo, Japan. OpenMP Terence Parr's http://aramis2.obspm.fr/coulais/. Robbie (GCC >4.2) Paul Wessel's Barnett's ANTLR Jaffey, A., M. Cheung, and A. Kobashi, 2008: Online data analysis using Web GDL. multithreaded GDLffDICOM grammar description GSHHS AGU Fall Meeting 2008, San Francisco, USA. http://www.agu.org/meetings/fm08/. shorelines Image matrix parsers Jaffey, A., A. Kobashi, and M. Cheung, 2009: GPU acceleration of the scientific data etc Magick's op. GDL displaying MODIS satellite image analysis package GDL. NVIDIA Research Summit 2009, San Jose, USA. Magick++ http://www.nvidia.com/object/gtc 2009 archive.html. Matthew (stored in a HDF file) on multiple X11 readline GNU Craig's windows - using a true-color RGB zlib GDL used for analyzing LIDAR data (reading Acknowledgements ... autotools TeXtoIDL GDL-generated PostScript plot of a Fourier composite, and using separate channels. netCDF files, producing PostScript plots) on spectrum in a LaTeX-generated PDF file. Presentation of the poster during the EGU conference in Vienna was supported by the free, open & libre: PLplot , using the IDLWAVE mode for Emacs. European Geosciences Union (through the Young Scientist’s Travel Award for (mandatory) 2D & 3D plots, th PythonPython Europeans) and the European Commission’s 6 FP IP EUCAARI (European Integrated contours, surfaces, text (optional) calling Python Supported platforms and availability of pre-compiled/pre-configured packages project on Aerosol Cloud Climate and Air Quality interactions, no. 036833-2). Thanks annotations code from GDL & are due all volunteers who helped in the development of GDL by providing their feedback etc (for development only) GDL as a Python wxWidgets in the form of patches, bug reports, support requests and comments. Development of module Packaged versions of GDL are available for several Linux distributions GDL is hosted at SourceForge. The LIDAR figure was provided by Michał Piądłowski. free & open: (incl. Fedora, Gentoo and Debian) and Mac OS X (e.g. via Macports and (optional) Disclaimer Fink). The source code (available at http://gnudatalanguage.sf.net/)

GDL is not an official GNU package (yet). IDL is a registered trademark of ITT Visual TM compiles on other UNIX systems, including BSD, OpenSolaris. TM Information Solutions (http://www.ittvis.com/).

Poster presented at the European Geosciences Union General Assembly 2010, May 2010, Vienna, Austria (ESSI1 session: Earth & Space Science Informatics / International Geoscience Informatics Partnerships, Projects, and Collaboration Technologies)