On Aug 23, 2012, at 2:37 PM, Randy Horne <[email protected]> wrote:

> 
> What is the “generally accepted” approach for how a specific quality flag 
> value should be assigned for a corresponding data value (in the corresponding 
> data variable) that has a _FillValue ?
> 
> Is it sufficient that, because the data variable value is _FillValue, the 
> corresponding quality flag value can be undefined ?

I do want to mention one variant to consider:  if the quality of a particular 
point is the *reason* that the data value is _FillValue, then it is useful for 
that corresponding quality flag to retain its value.  We use this approach in 
our Data Quality Screening Service, which allows users to filter (some of) our 
satellite data based on the quality flags.  In the output product, we replace 
data values with _FillValues if the quality flag indicates it does not meet 
specified quality criteria, but then we retain the quality flag so that the 
user will know WHY that particular point has a _FillValue (vs. not being able 
to get a retrieval at all).
--
Dr. Christopher Lynnes, NASA/GSFC, Code 610.2, 301-614-5185

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