[daip] VLBAUTIL vlbapcor procedure

[Amy Mioduszewski]

Dear Yuri,

I changed the interpolation for VLBAPCOR because a user DID see differences 
between sources and had weird interpolation effects.  Also, you will see if you 
do a HELP CLCAL, 'SELF' now uses all the data for each source and interpolates 
across scan boundaries.  Have you had a problem with the current version, if yes 
that is most likely a bug with CLCAL not VLBAPCOR.  If so please send details of 
your specific problem.

Amy

Yuri Y. Kovalev wrote:
> Colleagues,
> 
> There was made a change in the way how PCAL solution is applied in the 
> VLBAUTIL procedure vlbapcor.
> Until AIPS version 31DEC06 inclusive a default interpolation was used.
> Starting with 31DEC07 the interpol 'self' is applied:
> %%% Part of the VLBAUTIL 31DEC07 code:
> if vba_ok >=0 then
>   type 'run pccor'
>   task='pccor'; default; tget vlbapcor;task='pccor'
>      delcorr 0; runwait('pccor')
>   if(vba_frg>0)then
>     type 'run sncor'
>     task 'sncor';default; tget vlbapcor;task 'sncor'
>       snver=MAXTAB('SN');opcode 'zphs';timer 0; sour ''
>     runwait('sncor'); opcode 'zdel';runwait('sncor')
>   end
>   type 'RUN CLCAL'
>   task 'clcal';default; tget vlbapcor;task 'clcal'
>      gainv gainu; gainu=MAXTAB('cl')+1; snver=MAXTAB('SN')
>      interpol 'self'; calsour '';timer 0; ante 0;runwait('clcal')
>   vba_sn=snver
>   vba_cl=gainu
> end
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> I believe that this change can be potentially dangerous.
> In case when a short scan is observed, no PCAL value might exist for a 
> given short-scan source and interpol 'self' might deliever proper result.
> 
> I also see no specific reason why PCAL soulitons should be applied on a 
> source by source basis (interpol 'self'). There must be no or very 
> little dependence between the instrumental phase and different sources 
> observed.
> 
> I suggest that you correct the vlbapcor back to the default 
> interpolation in the task 'clcal'.
> 
> Cheers,
> Yuri.
> 
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