[Difx-users] New to DiFX - issues with test dataset rdv70

[Rebecca Lin]

Hi all,

Thanks for all the responses!

I compared the new reference_1.* and example_1.* files provided with my
outputs and got consistent results!

I currently have DiFX set up on CITA servers and have DIFX_MACHINES set to
point to a setup file containing the following:

version = 1
homard, 2, 16

However, when I run startdifx, only 3 nodes were generated in the machine
file instead of the required 8 to run the rdv70 test set. I'm not sure how
else to set up the cluster definition.

I'm hoping to understand how DiFX uses the delay information generated by
calc as I'm interested in providing my own delay solution in the future.
I'll give the model.h/model.cpp and Mode class a look for now.

Best,
  Rebecca

On Fri, 13 Aug 2021 at 02:25, Reynolds, Cormac (S&A, Kensington WA) via
Difx-users <difx-users at listmgr.nrao.edu> wrote:

> On a technical note, how exactly is that (un)correction of the
> atmosphere done for ALMA? calc11 has knobs to switch the dry and wet
> atmosphere components off, but I don't see how to do it for just one
> antenna (i.e. you have them on for all antennas or off for all). How do
> you get ALMA to be treated differently to the rest of the array?
>
> I ask because we had a case recently where the atmospheric corrections
> were accidentally left in for the ATCA tied array. I came up with a
> kludged method to switch them off in DiFX for just ATCA, but if there
> is a more standard solution that would be much preferable.
>
> thanks,
> Cormac.
>
> On Thu, 2021-08-12 at 11:27 -0400, Geoff Crew via Difx-users wrote:
> > Yes, one effectively has an average signal with some average of
> > corrections.
> >
> > (Fortunately no one has requested us to go to second order to sort
> > that
> > out, as it's intractable.)
> >
> > On 8/12/21 8:43 AM, Rodrigo Amestica via Difx-users wrote:
> > > if in ALMA the DRY and WET corrections are applied per antenna, how
> > > could
> > > them be uncorrected from the phased VLBI station signal? Perhaps an
> > > average
> > > value can be calculated for the ALMA station as a whole?
> > >
> > > ps: I hope that my question helps for completness, without steering
> > > away
> > > from the original posting.
> > >
> > > On Thu, 12 Aug 2021 08:08:58 -0400 (34 minutes, 3 seconds ago),
> > > Geoff Crew via Difx-users <difx-users at listmgr.nrao.edu> wrote:
> > > > For completeness:  an array using Calc (e.g. ALMA) for its delay
> > > > model
> > > > ends up having made these corrections; these must then be
> > > > uncorrected
> > > > in the VLBI correlation.
> > > > On 8/11/21 11:02 PM, Adam Deller via Difx-users wrote:
> > > > >   * DRY and WET refer to specific sub-components of the delay
> > > > > model
> > > > > (the dry and wet troposphere, respectively.) You don't need to
> > > > > worry
> > > > > about those - they are just there in case for some reason a
> > > > > user
> > > > > wants to undo the default calculations of these contributions
> > > > > to the
> > > > > delay model in post-processing and re-apply their own. (Mostly
> > > > > used
> > > > > by geodesists.)
> > > > --
> > > > Geoff Crew
> > > > gbc at haystack.mit.edu
> > > > _______________________________________________
> > > > Difx-users mailing list
> > > > Difx-users at listmgr.nrao.edu
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> > >
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>
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