[daip] problems with vlant

[Eric Greisen]

bob at physics.ucdavis.edu wrote:
>> bob at physics.ucdavis.edu wrote:
>>> hi, i ran vlant by mistake on a file that shouldn't need it.
>>> much to my surprise vlant came back with inappropriate changes
>>> to baselines. below is the information. the changes it found occured
>>> about
>>> 8 months after the observations were taken.
>> VLANT looks at all changes to antenna locations entered due to baseline
>> runs that FOLLOW the observing run.  If they affect antennas at stations
>> that you used, they are assumed to be improvements on those station
>> locations from the values used during your run and entries are made in
>> the CL and AN tables accordingly.  It is correct that a baseline change
>> AFTER you observed should be applied to your data.
>>
>> Eric Greisen
>>
> hi, looking at the baseline database, i see that the two that were
> applied have blanks in the ant move column!
> 
> bob becker

You are letting yourself be confused by this business - it confused me 
which is why I wrote VLANT.  If some antennas move at a date after your 
run, operations runs a full baseline run.  The results of that may be to 
suggest a correction to the location of an antenna at some station that 
did not move - i.e. that was used in your run.  VLANT is written to find 
these and update your phases for the improved station locations.  It 
only updates for changes in which the antenna number and the station ID 
both match those of your observations.  (Actually it looks deeper than 
that to avoid the case where an antenna moves away from a station and 
then comes back years later.)

ERic Greisen