[fitsbits] start of Public Comment Period on the INHERIT convention

[Frank Valdes]

This is a programming practices question.  In our case we want applications to be independent of the data format structure (possibly not even FITS).  An application asks for the value of EXPTIME in an image (a higher level construct which might happen to map to extension 10 in an MEF).  The lower level image I/O software (layered on even lower level FITS I/O in this discussion) handles this.  What you are saying is that high level application software needs to deal with the format itself.  I would pose the question, why doesn't your application open a FITS file as a binary file and do all the parsing of the file rather than rely on a FITS I/O layer such as CFITSIO, etc.  That would certainly be explict right? :) [I really assume  and hope that you use some FITS library to get a keyword and not direct file access to get your keywords.]

But if you are saying why doesn't the lower level FITS I/O layer just check both then basically this becomes the INHERIT implementation, right?

Frank


On Jul 2, 2015, at 9:43 AM, Phil Hodge wrote:

> What I don't understand is why you need to "inherit" these keywords.  For DECam you have a convention that some keywords are in the primary header and some are in an extension header.  Why not just read or update keywords in the headers that actually contain the keywords? That's what we at STScI do for HST data, in spite of the INHERIT keyword.  Explicit is good.
> 
> Phil
> 
> On 07/02/2015 12:08 PM, Frank Valdes wrote:
>> I will respond with the DECam raw data from the telescope.  This is a good question for this discussion.  If this goes somewhere interesting I can look at the other NOAO mosaic cameras and the calibrated files.
>> 
>> The keywords from the list at http://heasarc.gsfc.nasa.gov/docs/fcg/standard_dict.html that are inherited are:
>> 
>> DATE-OBS, INSTRUME, OBJECT, OBSERVER, TELESCOP
>> 
>> I might also mention a couple that are important but not on the list:
>> 
>> EXPTIME, FILTER, RA, DEC
>> 
>> There are no WCS keywords even from the advanced WCS papers or the TPV convention used by DECam.
>> 
>> Frank
>> 
>> 
>> On Jul 2, 2015, at 7:26 AM, Mark Calabretta wrote:
>> 
>>> On Wed, 1 Jul 2015 11:30:12 -0700
>>> Frank Valdes <valdes at noao.edu> wrote:
>>> 
>>>> DECam is
>>>> generating a huge amount of data (arguably the biggest optical data
>>>> source in the world) on an almost daily basis.  The raw data is an
>>>> MEF and uses INHERIT.  The calibrated data produces MEF with INHERIT.
>>>> All mosaic data that NOAO has in its archive, -- >10 yrs of Mosaic, > 5
>>>> yrs of NEWFIRM, DECAM -- is in this format.
>>> Which keywords known to the FITS standards are these files inheriting?
>>> 
>>> 
>>> Mark Calabretta
>> 
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