Re: [netcdf-java] uv component data compression

Hi antonio:

Most grib data from ncep is scaled/offset to an integer and then jpeg000 wavelet compressed. CDM can read but not write this format.

Your best bet is to get the floating point out of the CDM, subset just what you need, and compress it when sending to your client. Standard would be to decide how many bits of accuracy you need and convert to integers with that precision, then bzip2 or deflate.


On 1/30/2013 12:43 PM, Antonio Bleile wrote:

I am currently trying to read the uv height over ground data of the GFS
model, e.g. "gfs.t00z.master.grbf00.10m.uv.grib2". The file's size is
roughly 400k. When I decompress the uv float arrays and save them as
zipped files I get roughly a file of 1MB (uncompressed 2MB). I suspect
the compressed grib data is somehow stored as 2 byte float perhaps? As
I'm very unfamiliar with the netcdf library I'd like to learn more about
how the data is compressed and decompressed within the grib file. The
motivation of all this is that I'd like to display the UV data on an
android device (which has insufficient resources to run netcdf library!)
so I need to convert the grib compressed data into something more simple
but yet efficiently compressed! I'd appreciate any pointers to the right
documentation or any hints on how the uv data is compressed....



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