IDL, a tool for oceanographic data visualization and analysis

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IDL, a tool for oceanographic data visualization and analysis

Under the scorching sun of Perpignan, in the heart of the French Pyrénées, next to the Spanish border, a team of oceanographic researchers is developing a software for the visualization and analysis of oceanographic data using several instruments (i.e., CTD (Conductivity-Temperature-Depth), current meters, sediment traps, and optical and meteorological sensors) that are simultaneously deployed in several points.

Searching for a common language

At the beginning of 1999 Ms. Dimitra Kitsiou, a post-doctoral researcher, was hired by the Centre de Formation et de Recherche sur l'Environnement Marin, the CEFREM, to develop a software for the visualization and space- and time-related analysis of miscellaneous oceanographic data.

At its inception, the project resembled the tower of Babel. Many research centers acquire oceanographic data on a permanent basis, which is then archived, shared and analyzed by scientists all over the world. However, these data are saved in several formats and users work with all kinds of operating systems; therefore, every time data are transferred users are faced with tricky reading and compatibility issues.

Finding a multipurpose tool

Ms. Kitsiou thus set out to develop a tool for reading oceanographic data.

"In oceanographic studies," says Ms. Kitsiou, "researchers are interested in data as varied as temporal series of winds, currents, temperature, biological and chemical parameters of water, particle flows, etc. For this reason, different types of instruments are used simultaneously and, therefore, many types of data are recorded. Finally, because many laboratories work on joint projects, these data are often saved in differing formats. The result is hindered data access and analysis. We needed software that would read, visualize, and analyze any type of data, in all existing environments. We also wanted our work to include (scale and vector) cartography and animation. The latter would enable us to easily visualize long-term changes in the marine environment."

The CEFREM's project was designed in cooperation with the Barcelona Marine Sciences Institute and follows the VADO (Visualization and Analysis of Oceanographic Data) program. Each operating system environment is represented: Perpignan works on Macintosh and Windows and Barcelona runs on UNIX. Files are in ASCII format and are as big as several hundred kilobytes.

...and easy to use

"We needed a software that was very user-friendly! Our users are not information technology experts," adds Ms. Kitsiou. "When I arrived here, there were routines in two different languages, IDL and FORTRAN. We have decided to keep only IDL (Interactive Data Language) because it is easier to use and faster for data visualization. IDL is not only easy to use when learning to create routines, it is user-friendly in all its features."

Free access to the Internet

"My role is to develop a standard software application, a multipurpose tool for analysis of two- and three-dimensional visualizations for any oceanographic data, wherever they originate from. Thanks to IDL, we're almost there. Ultimately our vision for this application goes further. We want to allow free access to our software on the Internet."

Figure 1. Bathymetry map of the Mediterranean Sea.
	Figure 2. The form the user should fill in for each different file format in order to have access to the various data sets.
Figure 3. Zoom in the Gulf of Lions, France and visualization of the positions of the nine sampling stations of the High Frequency Flux (HFF) experiment.
	Figure 4. Information concerning the sampling sites selected by the user. For example, in the sampling station LINE 1 there is a sediment trap at 300m depth and a current meter at 165m depth. The recorded parameters are (a) the total mass flux and (b) the direction, velocity, temperature and pressure of the water mass.
Figure 5 (a). Time-series of temperature for LINE 1, 2, 3, 4 recorded from the current meters at 165 m depth. (b). Averaged time-series of temperature (NSUM=50) for LINE 1, 2, 3, 4 recorded from the current meters at 165 m depth.