QDOAS

QDOAS is the result of a collaboration in 2007 between BIRA-IASB and S[&]T, a Dutch company already well-known for the development of cross-platform products and software tools for the processing of satellites measurements (BEAT, VISAN...). As its predecessor WinDOAS, QDOAS is a very friendly user interface dedicated to the retrieval of trace gases from DOAS measurements. The user interface of QDOAS looks very similar to the WinDOAS one and the DOAS engine is the same.

Last release : 2.00, 5 March 2012

QDOAS S/W User Manual, 5 March 2012

Amazing : QDOAS in the world, 15 May 2012

Main differences between QDOAS and WinDOAS

The major changes are :

• QDOAS is a cross-platform implementation of WinDOAS i.e. Qdoas is portable to Windows and Unix-based operating systems (Unix, Linux, Mac, ...);
• configuration files are now in XML format, this means that WinDOAS and QDOAS configuration files are not compatible;
• there is a better separation of the code between the user interface and the engine (completely transparent for users);
• The graphical user interface is built on the Open-Source version of the QT-4 toolkit, a cross-platform application framework, and QWT plot libraries. QDOAS is also open source; the code is available on request and can be used under the GNU license agreement.

Another major improvement is that convolution, ring and undersampling tools are modules completely independent from the QDOAS main user interface. This means that the tools manage their own configuration files and that they can be called either from the user interface or from the command line. The package is completed by a powerful command line tool, doas_cl, that processes DOAS analysis, convolutes cross sections or calculates ring or undersampling cross sections according to the input configuration file.

In summary, QDOAS comes in five independent executables or modules :

• qdoas : the user interface similar to the WinDOAS one;
• convolution : a convolution tool;
• ring : a ring calculation tool;
• usamp : a undersampling calculation tool;
• doas_cl : a powerful command line tool that applies on qdoas, convolution, ring and usamp configuration files.

Other minor improvements between WinDOAS and QDOAS

About the user interface :

• The main sub-components of the GUI into resizable panels with a fixed arrangement;
  
• Tab-switched access for project/analysis windows settings and plotted results;
• All the spectral windows processed in one shot and tab-switched access between the different fitting windows;
• Configuration file in XML format (specific editors); this means that configuration files are not compatible between WinDOAS and QDOAS;
• A true management of spectra files in the project tree
• Possibility to set plot colour and style
• Interactive plot mode (zooming, overlay of an existing ASCII file, possibility to fix the scaling of the plot…) : for that, right click the title of the plot
• Export of plot in different portable image formats (png, jpg)
  

View of the QDOAS user interface

About projects properties :

• File format selection is now out of the instrument page in order to be able to constrain the selection of the fields in the display and output page.
• File formats are now distributed in two groups : ground-based and satellites;
• Only MFC standard format is supported for QDOAS; GOME2 satellite format is also operational in QDOAS;

Example of Project Properties configuration page

About analysis windows properties :

• Horizontal scrolling of options;
• Shift and stretch in nm units only;
• Hidden option in WinDOAS (expert mode) : concentration of a molecule constrained to the value found in a previous window