Hi Jonnie I have a couple questions - maybe can be discussed in a few minutes.
1. Just to be completely pedantic, is the fits command run "on" the output miriad file, or from the data in memory that was used to make the miriad file? In other words, should the "fits" line in Fig 1 be drawn as is, or from uvcRREM to uvcRREM.uvfits? 2. I'm confused by truncated values still containing many more decimals after the point where the two agreed. Is there some other operation that's happening to the data? I could see something like this happening if the data is split, then truncated, then phased. But the phasing happens before the data is split. Do both files store visibilities as real/imaginary parts, or does one do something like amplitude/phase? Sorry if these are silly questions -Adam On Wed, Mar 9, 2016 at 10:27 AM Peter Williams <[email protected]> wrote: > I may come up with more comments, but here are a couple right off of the > bat: > > The truncation effect is almost surely related to MIRIAD's default storage > of visibilities as 16-bit integers paired with a scale factor ... which can > be overridden, at a cost of disk space. The discussion of precision in > section 3 seems a bit inaccurate to me. > > Figure 1 is not fully correct. MIRIAD also supports the "uvfits" data > ordering ... and in fact this is preferred, since then you can perform > on-the-fly Stokes resampling when reading a file. But, for instance, early > ATA output files were in the format showed on the left side of the figure, > until I rewrote the data emitter to be better. > > Peter > > On Wed, 2016-03-09 at 12:00 -0500, Jonathan Pober wrote: > > Hi everyone, > > I attach a memo by Adam Lanman for posting to the HERA memo series. What > started as a simple task of reading PAPER data out of both MIRIAD and > uvfits formats revealed small, but non-trivial differences between the two > files. We've mainly been discussing this on MWA telecons, since they have > been the main users of the MIRIAD -> uvfits conversion, but I think the > final findings do reveal interesting things about our MIRIAD data > analysis. We can lead a short discussion of the findings during the HERA > data telecon in ~30 minutes. > > Cheers, > > Jonathan > >
