[fitsbits] Any bad pixel mask convention?

[William Thompson]

On 12/04/13 10:18, Eric Greisen wrote:
> Richard J. Mathar wrote:
>> Is there something like a bad pixel mask FITS standard that stores bad pixels
>> with a boolen value or perhaps a float where 1=good, NaN=bad in FITS images?
>> Should one use a BLANK value combined with a byte or integer image or is
>> it best to invent a private ASCII format for this purpose?
>
> Internally AIPS uses a magic value with its floating image data.  But we
> do once in a blue Moon hit a real value that is exactly the magic value.
>
> For FITS files we change this magic value into a NaN when we write out
> the files in floating point.  I doubt that integer is ever used now, but
> when it does we declare a blank value (e.g. -32767 in 16 bit) and scale
> the image to -32766 to +32766 and use -32767 for blanked pixels.

What do you mean that you doubt that integer is ever used now?  All our level-0 
data is stored in integer format, as it comes down from the spacecraft.

> Eric Greisen
>
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-- 
William Thompson
NASA Goddard Space Flight Center
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Greenbelt, MD  20771
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William.T.Thompson at nasa.gov