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[netCDF #VQZ-726653]: data packing

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  • Subject: [netCDF #VQZ-726653]: data packing
  • Date: Thu, 27 Sep 2007 14:56:40 -0600
Yes, the _FillValue should be the same type as the packed data.

But for the purpose of the packing formulas, the dataMin and dataMax
are assumed to include the unpacked _FillValue as one of the values of
"data".  In fact, it's legal (though not necessarily recommended) for
the unpacked _FillValue to be in the middle of the range of data. But
it's also possible for dataMin or dataMax to be equal to the unpacked
_FillValue.

The use of "data" is bad here, because it's not clear whether we're talking
about the actual physically meaningful data or the values stored in the
file.

So that's yet another source of confusion in the Best Practices advice
on packing and unpacking.  My only defense is that I didn't write
this, I inherited it.  When we've written an example, we'll rewrite
that section to try to make it clearer.

Thanks for pointing out the problems.

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: VQZ-726653
Department: Support netCDF
Priority: Normal
Status: Closed