Re: [cf-satellite] tiling schemes for netCDF4 gridded products covering irregular subsets of a hemisphere

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On 06/06/11 15:30, Horne, Randy (Contractor) wrote:
> Dear Sir:

Dear Randy,

> I am working a program where valid gridded data is restricted to the
> portions of the earth that are (1) land or sea, (2) day or night, and
> (3) clear or cloudy.
> 
> Substantial efficiencies are gained by storing only tiles with valid
> data.  For example storing land surface temperature in tiles that
> only are on land.

I am no expert on the matter, but I would store each set of tiles in a
different band, each having independent lon/lats. Otherwise, I am pretty
sure that netcdf4/hdf5 does a good job at compressing the data if large
areas of it are NaNs for example, so maybe it's worth trying ?

> In addition, there is substantial benefit in being able to read only
> those tiles from a hemispheric netCDF4 file that are requested by the
> user.  For example, the user may only be interested in land surface
> temperature over Argentina in a product that has land surface
> temperature for the entire western hemisphere.

That is a matter of programming I think: the program must be able to
explore and return the interesting data.

> A few questions:
> 
> (1) Does one or more existing set of netCDF4 conventions exist to
> provide these capabilities ?

> (2) If there is not an existing set of conventions, is anyone working
> on the conventions required to support these capabilities ?

The conventions are merely a naming scheme, nothing more. You can do
whatever you want with them, but the capabilities you are are requesting
are more programmatic...

Best regards,
Martin
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