Hi Mike,
> We're defining the metadata for our weather products and in some cases we're
> using global attributes such as one named:
>
> "total_number_pixels_for_ash_detection_overall_QF_high", type=int,
> value=120000
>
> This global attribute holds a count of the number of pixels for which a data
> quality flag is set to "high". It's straightforward. The units are built
> into the attribute name ("total_number").
>
> Would this be better defined using a variable and explicitly specifying the
> units?
Yes, I think a variable would be better than the global attribute.
> Here's another example: attribute name="minimum_ash_cloud_height_in
> kilometers" value="1.5" type="float".
> In this case I feel like a variable might be better, then we could give it a
> long name, units, valid min and max, etc.
I agree.
> Is there a rule of thumb when a variable is necessary vs. when a global
> attribute will suffice? Or did I answer my own question with the second
> example?
Here's the guidelines we provide in our workshop for when to use variables
versus when to use
attributes:
http://www.unidata.ucar.edu/netcdf/workshops/2011/datamodels/VarsVsAtts.html
But I think the most important consideration in this case is that you want to
attach units to
the value, which means you have to use a variable, because attributes can't
have attributes in
the netCDF data model.
--Russ
Russ Rew UCAR Unidata Program
address@hidden http://www.unidata.ucar.edu
Ticket Details
===================
Ticket ID: HPI-640345
Department: Support netCDF
Priority: Normal
Status: Closed
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