[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Netcdf4 Compound types and Examples




Any example you could contribute would be most welcome. They need to
run without command line arguments, and return a 0 when everything
runs correctly...

Thanks!

Ed
-- Ed Hartnett -- address@hidden
Okay guys, here is the "example" we are working on. A long time ago we put the World Ocean Database and the GTSPP data, all subsurface obs that we have or get, into the old HDF-EOS point structure. The way we had it structured was that each file was a 10-degree square with a name that contained the box number as in COADS. The HDF-EOS point structure had levels that made what was a series of flat tables look like a hierarchy by having a link field. So level 0 data would be all the box 2's in the box 10, and the level 1 data would be the data with the box2 number as the link field. This allowed you to search for all the data in a box2 efficiently
A downside was that the number of rows in the field had to be equal to the sum total of depths at which there were observations. This meant that there is a huge amount of empty space. So how might we improve on this - why netcdf4! We use vlen's to deal with the varying number of depths and a compound data type to combine together the info. Groups and (sub)-Groups provide the same structure that was "emulated" in the point structure. Or at least that was what we thought would be a good design given netcdf4's features, but that is what prompted my email about examples and design - there may well be better ways of doing this.
However, unless I miraculously find both money and a good C programmer, or get Fortran wrappers to work, it will be sometime before it happens.
BTW, at one point I used the hdf4tohdf5 program to convert these files to HDF5, so they can be read using that library. I don't know that the conversion worked that cleanly to use with the HDF-EOS5 library, but it should be possible to both read and write using the libs that are a part of Netcdf4. I actually had a few days to begin to work on this, hence the series of emails. 

-Roy




**********************
"The contents of this message do not reflect any position of the U.S. Government or NOAA." 
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division 
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097

e-mail: address@hidden (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/

"Old age and treachery will overcome youth and skill."