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Tuesday, August 10, 2010

svp_tool WOD query tool

I spent some time coding on the weekend (which would be considered sad by many, but not by me) and built a simple push button GUI interface that allows the user to refine WOD queries by instrument and month.  If I wasn't limited by the X interface, I'd add more SQL type functionality and allow for queries on any field (year, cruise ID, etc).  More work in the future I guess.  Here's a screen shot of the button bar that allows the user to choose instrument type and month of observation, the top row is for the month, the bottom row is for instrument type.  The labels on the buttons switch to UPPERCASE when selected and back to lowercase when deselected.  The query is only done after a geographic selection in the map window.  I've shown an example of several hundred CTD casts collected in the months of July, August and September in the Northwest Passage in northern Canada, one of my favourite areas that I've ever worked in.

The CTD data is plotted in the main SVP Tool window above, with sound speed, temperature and salinity plotted versus depth (left to right, respectively).

More work?  Of course.  If I turn on the debug mode of the WOD query engine, I can see that it spends an awful lot of its time unzipping the raw source data for each WMO square that it visits during the query extraction.  I'm still looking to speed this up if i can, right now the code fires off a system('gunzip -c file > tempfile'); whenever it hits a zipped WOD file.  I'm curious if it would be faster to run through zlib instead?  Kurt had also suggested converting the WOD files to a binary format so that's another option that would guarantee to bear some fruit but I really do like the elegance of sticking with the raw WOD files (easy to update, no need to reconvert with each update).  More thinking needs to be done, obviously...  Suggestions are welcome.

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