Greetings!
For our CONUS grids, we make use of "sparse grids" in our netCDF files.
From <http://cimms.ou.edu/~lakshman/WDSS2/dataformat.shtml> (about
halfway down the page), our/the netCDF sparse grid format can be
described as:
If your data are sparse, you can save a whole bunch of space by saving only the
non-missing data in a simple run-length encoded format. The global attributes
and the other variables are the same as the regular formats. However, the
dimensions are provided by pixel_x, pixel_y for the first two dimensions and
run_length for the number of values in a run (default=1 if run_length is
omitted). The original dimensions are also required even if no variables
actually use them. The default background value is MISSING_DATA unless a
different value is provided (see the SparseRadialSet example below).
Example of a sparse lat-lon-grid:
dimensions:
Lat = 650 ;
Lon = 700 ;
pixel = 23541 ;
variables:
float Reflectivity_0C(pixel) ;
Reflectivity_0C:Units = "dBZ" ;
short pixel_x(pixel) ;
short pixel_y(pixel) ;
int pixel_count(pixel) ;
// global attributes:
:TypeName = "Reflectivity_0C" ;
:DataType = "SparseLatLonGrid" ;
:Latitude = 37. ;
:Longitude = -100. ;
:Height = 0. ;
:Time = 990376569 ;
:FractionalTime = 0.584999999999127 ;
:attributes = " ColorMap Unit" ;
:ColorMap-unit = "dimensionless" ;
:ColorMap-value = "Reflectivity" ;
:Unit-unit = "dimensionless" ;
:Unit-value = "dBZ" ;
:LatGridSpacing = 0.01 ;
:LonGridSpacing = 0.01 ;
:MissingData = -99900.f ;
:RangeFolded = -99901.f ;
I haven't dug far enough yet to see much on netCDF sparse grids.
Considering that we were able to reduce a CONUS grid from 71 Mb to 4 Mb,
we would like to continue to make use of sparse grids if we can.
Can anyone offer some guidance whether we can use THREDDS with sparse
grid data? If we can, do I attempt to specify my coordinate
transformations in the header, or is there more manipulation that I need
to do on the data?
Thanks!!
-kevin.
--
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Kevin L. Manross | ** New Address **
CIMMS Research Associate | 120 David L. Boren Bvd
NSSL : WRDD : SWAT | Rm 3923
<kevin.manross@xxxxxxxx> | 405.325.6385
www.cimms.ou.edu/~kmanross |
"My opinions are my own and not representative of
CIMMS, NSSL, NOAA or any affiliates"
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