[Difx-users] How to read difx2fits output

[harro verkouter]

Hi all,

For the verification of sfxc postprocessingtools (to generate e.g. FITS-IDI
files) we have a comparisontool for the meta-data. The one for numerical
equivalence of two FITS-IDI files is currently lacking (it does work for
MeasurementSets):

https://code.jive.eu/verkout/jive-toolchain-verify

Specifically look at the ‘compare-ms-idi-meta.py’ script. Despite it’s name
it can compare any number of FITS-IDI and/or MeasurementSet files -
including zero of either 😄

Cheers,
h

Op zo 29 aug. 2021 om 10:17 schreef Adam Deller via Difx-users <
difx-users at listmgr.nrao.edu>

> Hi Rebecca,
>
> I have a script called fits_compare.py that diff's two FITS-IDI files that
> are supposed to be identical (i.e., same antennas, integration time, etc).
> It was always a bit of hack/check code and is probably not very user
> friendly.  If you want I can put it on github so you can get it - it also
> has a dependency on some helper functions that are available in
> https://github.com/dingswin/psrvlbireduce/, but there's every chance that
> it won't work out of the box and I don't have any time to debug it at the
> moment.  But let me know if you'd like me to make it available and try
> investigating it.
>
> Cheers,
> Adam
>
> On Sun, 29 Aug 2021 at 07:57, Rebecca Lin via Difx-users <
> difx-users at listmgr.nrao.edu> wrote:
>
>> Hi Leonid,
>>
>> Thanks for pointing me to the documentation! I'm hoping to compare
>> visibilities from my correlation pipeline to the output from DiFX.
>>
>> Best,
>>   Rebecca
>>
>> On Sat, 28 Aug 2021 at 13:16, Leonid Petrov <Leonid.Petrov at lpetrov.net>
>> wrote:
>>
>>> Rebeca,
>>>
>>> > I'm wondering if there is documentation on how information is stored
>>> in the
>>> > fits file
>>>
>>>   Sure:
>>>
>>> ftp://ftp.aoc.nrao.edu/pub/software/aips/TEXT/PUBL/AIPSMEM114.PDF
>>>
>>> > and how to plot the visibilities.
>>>
>>>   Usually, these plots are useless. There are exceptions, but generally,
>>> you need process the data first to see any signal. You can develop your
>>> own software for visibility analysis or try to use existing packages,
>>> whichever you prefer. But it is not easy. Depending on the problem,
>>> mastering data analysis may take from months (though this sounds
>>> very optimistic) till ... all your life. Good luck.
>>>
>>> > I'm mainly wondering where the
>>> > complex visibilities are stored in the fits file.
>>>
>>>   In section UV_DATA. See AIPSMEM114.PDF for details.
>>>
>>> Leonid
>>> 2021.08.28_13:09:41
>>>
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>
>
> --
> !=============================================================!
> A/Prof. Adam Deller
> ARC Future Fellow
> Centre for Astrophysics & Supercomputing
> Swinburne University of Technology
> John St, Hawthorn VIC 3122 Australia
> phone: +61 3 9214 5307
> fax: +61 3 9214 8797
>
> office days (usually): Mon-Thu
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