Re: [netcdf-java] Writing unsigned data to attributes

On 7/2/2013 5:52 PM, Alex Fraser wrote:
Hi John,

Thanks for the detailed explanation.

----- Original Message -----
From: "John Caron" <caron@xxxxxxxxxxxxxxxx>
3) a valid range is applied to the underlying data, before anything
else happens. [...]

Is the same true for _FillValue? In that case I think I can use the following 
rules for unsigned variables:

  - When specifying a fill value, use the same data type
    as the variable and allow it to be written signed;
    nc4 IOSP demands this.
  - When specifying a valid range, promote the data type
    (e.g. byte -> short).

For example, the following should be equivalent:

byte Band1(y, x);
    Band1:_Unsigned = "true";
    Band1:_FillValue = -1b; // byte

byte Band2(y, x);
    Band2:_Unsigned = "true";
    Band2:valid_range = 0s, 254s; // short

Is that right?


Hi Alex:

Yes, that should work.

We may need to describe this in the user manual, so other libraries implementing scale/offset/missing values will do the same thing.

If anyone on these lists have further opinions, they would be welcome before we standardize on it.


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