En:idl tool


SHOM-Ifremer wave analysis tool


IDL installation

For the runtime licence, you need to register first at http://www.exelisvis.com/login.aspx?ReturnUrl=%2fMyAccount.aspx to dowload what is called the "IDL Virtual Machine". Follow this link to the IDL official website (it's free but you need to create an account). We are currently working with IDL 8.1. Please use this version to avoid conflicts.

Under linux, just do:

sudo mkdir /usr/local/exelis
sudo ./install.sh

Under windows, just execute the install.exe

You can also request a free demo licence for IDL, if you want to develop the tool and test some new ideas.

Once installed, you can execute the idl tool using the runtime idl software.

You may be interested to know that there is a gnu-version of IDL: GDL under development. We have not yet tested it with our tool.

TWIST download

You can find all the necessary files on our ftp in the folder [1] If you have an IDL licence you can dowload all the *pro files. If you do not have an IDL licence, you should use the IDL runtime version (see above). In that case you will only need the file [ ftp://ftp.ifremer.fr/ifremer/ww3/TOOLS/IDL/rt_visumain.sav ] and the text file [ ftp://ftp.ifremer.fr/ifremer/ww3/TOOLS/IDL/TWIST_init.txt ]

TWIST is now under version control (starting with revision 90). If you have an extranet account on our server, here is how you can install it for the latest up to date version, which will be up to date.

  svn checkout --username your_Ifremer_extranet_login https://forge.ifremer.fr/svn/ww3tools/trunk/IDL


In order to facilitate the adjustment to your system settings (file paths, window size ...) you can configure the TWIST tool by editing the TWIST_init.txt which should be placed in the same directory as the *.pro files and /or the *sav file .

In particular, you may have to change the path for the default color palette  : palettes/doppler_modified_land_2.ct

Running idl and TWIST

Before you get started, you should know that TWIST will work with a graphics user interface (GUI) but it will also give you some text information in the command window from which you started it. So keep that window open and ready in case you need to read that information.

If you do not have an IDL licence you can:

  • Use the demo version (limited to 7 minutes, no output files capabilities): Then just start IDL in the directory where you have all the *.pro files, and type @visu on the IDL command line.
  • Use the free runtime runtime licence. Under Windows, click on the rt_visumain icon. Under linux, you can type this in a terminal idl -rt=rt_visumain.sav

The TWIST tool

This graphics interface was designed to facilitate the analysis of modelled and observed time series of wave data (spectral or not) and their comparison, as well as the display of wave parameter maps computed by wave models. In particular you can play with wave data by sliding the frequency and time "sliders" (bottom right) and go quickly from scatter plot to time series ...

Here is the way it looks :

Appearance of the TWIST interface when starting

The tools works in the following way:

  • read in a data file (time series, map …)
  • choose the plotting method
  • adjust parameters (date, time range, type of plot, palette)
  • save the plot (eps, png, gif, jpeg … ) or the data (ASCII file from NetCDF ...)

Some of the adjustements of the plotting parameters (like changing the time using the bottom right slider “time”) will automatically refresh the plot. For some other adjustments you may have to click on the “Refresh” button above the main window.

Also, because the tool is a clunky “under development” thing originally designed for personal use, it still has some bugs. If you are using an IDL licence (demo or full licence), no problem, just type .comp rt_visumain on the IDL prompt and correct the action that led to a bug. If you are using runtime IDL … well the system will stop… and you have no other solution that restart and avoid the action that led to a bug. Please report these bugs and we'll try to clean them up.

How to use some of the tool capabilities

Time series analysis

Plotting maps: regular grids

Plotting maps: triangle-based meshes