Re: [fitsbits] Start of the FITS-IDI Convention Comment Period
- From: Harro Verkouter <verkouter@xxxxxxx>
- Date: Tue, 2 Jun 2009 10:51:41 +0200
Hi all,
After reading through the document I'd like to make a few comments. Some of those apply to the implementation of the/a reader, nonetheless they seem to indicate incompatibility between documentation and practical use-cases. This is written from the perspective of the EVN FITS-IDI data-export software, which has been implemented exactly following the Flatters(1999) document [and thereby finding discrepancies between documentation and implementation].
* I have noticed that in most cases the order in which the keywords are written (also the non-mandatory FITS keywords) may have to be identical as in the documentation or else your FITS-IDI file may be rejected. I do not know if this situation has changed over the last few years, I did not experiment with writing keywords "out-of-order" since finding out that it most likely 'breaks' your FITS-IDI file.
* The "SORT" optional keyword to the UV_TABLE header (p.15) does not seem to get honoured. Our FITS-writer writes the hard-coded value "TB" (Time-Baseline) since that is the order in which the data is forcibly written, nonetheless it is never recognized by the reader, making the user have to run uvsort (or wossname of the task) to make the data recognized as being sorted in TB order. It may well be that this behaviour is triggered by our FITS-writer doing something else wrong however it is not documented - making it quite unfixable yet.
* I'm glad to see the POLARX/Y situation being somewhat resolved. I beg to differ, however, from the statement in the document "The units were changed from the meters specified by the earlier documents, but seldom used in actual implementations.". Especially since it is exactly this early misdocumentation (documentation says "meters", s/w interprets them as "arcseconds") that has caused many of our users headaches (EVN data).
Cheers,
harro verkouter
On Jun 1, 2009, at 20:53 , William Pence wrote:
This is to announce the start of the 30-day Public Comment Period on
the FITS Interferometry Data Interchange (FITS-IDI) Convention for the
interchange of data recorded by interferometric telescopes, particularly
at radio frequencies and very long baselines. This is the 16th in a
growing series of conventions submitted to the Registry which is
maintained by the IAU FITS Working Group.
Detailed information about this convention and a sample FITS file that
uses it are available for public review and comment from the FITS
registry web page at
http://fits.gsfc.nasa.gov/fits_registry.html
Comments about this convention may be posted here on the FITSBITS mail
exploder or the mirrored sci.astro.fits newsgroup. Minor typographical
issues may be sent directly to the authors of the convention.
Bill Pence
(on behalf of the IAU FITS Working Group)
--
____________________________________________________________________
Dr. William Pence pence@xxxxxxxxxxxxxxxxxxxxxx
NASA/GSFC Code 662 HEASARC +1-301-286-4599 (voice)
Greenbelt MD 20771 +1-301-286-1684 (fax)
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