Re: "xyt volume" function operation

[Jonathan Callahan <Jonathan.S.Callahan@xxxxxxxx>]

Ben,

The different 'views' available in LAS reflect the axes present in the final output product.  All of the products available with the 'xyt volume' view will contain X, Y and T axes (e.g. an XYT grid of daily global sea surface temperature).  This accounts for all of the 'xyt volume' products being data downloads and not visualizations -- LAS cannot yet create movies.

All 'xyt volume' products will be generated from a single variable defined on an XYT or XYZT grid.  This variable may be stored in a single, multi-dimensional NetCDF file (the preferred method) or you may use aggregation to string together files that represent temporal snapshots.  There are two ways to aggregate snapshot files for LAS.

1. use Ferret descriptor files
   http://ferret.pmel.noaa.gov/Ferret/LAS/FAQ/descriptor_files.htm
2. use the OPeNDAP aggregation server
   http://www.opendap.org/server/agg-html/
   

If you have total control over your data management and your files are not huge my recommendation is to store the entire time series for a single variable in a single file.  But I realize that most systems that produce data prefer to write multiple variables into snapshot files so aggregation is often required when setting up LAS.


-- Jon


benb wrote:

Hello All,

Can someone please explain how the "xyt volume" function (in Select view) wo
rks in LAS?

The output appears to go into a single NetCDF file (if "NetCDF file" is chos
en in "Select output"), but where does the input come from?

Can the input be a series (many) different files, or does all of the input h
ave to come from a single NetCDF file?  If it can be a series of files, how 
does LAS know what files (file names) to read to get the data?  Are the file
 names in the XML file that provides the content for the menu applet page?  
Does LAS figure out the series of file names (perhaps based on one example, 
and knowing the time interval of the files)?  

How does this work?  Also, can someone point me to the documentation on how 
to set this up?

Thanks very much,

Ben