[daip] redundant data points from VLBA distribution file

[Michael Bietenholz]

  I just noticed something wierd: there are redundant (doubled) data
points in my uv-data file.  The uv-file was loaded via FITLD from VLBA
distribution tapes, and I haven't done anything to it that should have
produced any additiona visibilities (UVCOP once to get rid of low
weights).  See UVPRT output below.  I could presumable get rid of
these by running UVAVG(OPCO=MERG) but it seemed odd that there were
any redundant data points.  They constitute only ~10^-5 of my data,
but they cause FIXWT (and possibly other things) to die.  Should I
worry?

       thanks,
            michael bietenholz


--- UVPRT output ----


File = GB042C C    .WTCLP .   1   Vol = 1    Userid = 1477     Channel =    1     IF =  1
Ref freq=  4.971552500 GHz  Ncor=  4  No. vis=      4528  Sort order= TB
U, V, W are in Kilo wavelengths at the reference frequency
Weights have been multiplied by     10.0000

Source M81      (    0)  RA   =  09 55 33.17  DEC  =  69 03 55.1
M81      Freq=  4.971552500 Sort= TB      1  RR          1  LL          1  RL          1  LR
   Time      Ant   U(Kilo)  V(Kilo)    Amp Phas Wt    Amp Phas Wt    Amp Phas Wt    Amp Phas Wt

 1/03:15:41  1- 5  -18712.   19234.   0.001  81 33   0.001 -87 33   0.001 148 33   0.000-123 33
 1/03:15:44  1- 5  -18715.   19230.   0.001 122 33   0.001 -28 33   0.000  86 33   0.000 128 33
>1/03:15:47  1- 5  -18717.   19227.   0.000  -9 33   0.000  31 33   0.001 122 33   0.000 -96 33
>1/03:15:47  1- 5  -18717.   19227.   0.000  -9 33   0.000  31 33   0.001 122 33   0.000 -96 33
 1/03:17:59  1- 5  -18831.   19057.   0.000 109 33   0.001  48 33   0.000 -56 33   0.000  36 33
 1/03:18:02  1- 5  -18834.   19053.   0.000 -20 33   0.000-110 33   0.000 -84 33   0.001-112 33
 1/03:18:05  1- 5  -18836.   19049.   0.000 159 33   0.000  86 33   0.000 157 33   0.000  26 33
 1/03:18:08  1- 5  -18839.   19045.   0.000 120 33   0.000 -69 33   0.000  88 33   0.000 -98 33


Probably the relevant part of the HIstory....

   410  FITLD RELEASE= '31DEC02 ' /--------------------------------------------
   411  FITLD OUTNAME='            '   OUTCLASS='      '
   412  FITLD OUTSEQ=    0   OUTDISK=  7
   413  FITLD SCLVIS =    1.08991 / Correlator scaling value
   414  FITLD DIGICOR =   1 / VLBA correlator digital corrs
   415  FITLD / FFT artifact corrections no longer necessary
   416  /--------------------------------------------------------------------
   417  /Begin "HISTORY" information found in FITS tape header by FITLD
   418  FITLD BLOCKED =                    T /
   419  FITLD FXCORVER= '4.22    '           /
   420  FITLD OPENED FITS FILE : 2002JUN26 19h58m43.95s
   421  FITLD SOFTWARE DIR : /home/fxcorr/code
   422  FITLD CORREL SOFTWARE VERSION : 4.22
   423  FITLD CORREL ON_LINE  : Motorola MVME167
   424  FITLD VXWORKS VERSION : 5.3.1
   425  FITLD LOG FILE : /home/fxcorr/logs/v47c020626:1638.log
   426  FITLD OBSCODE : GB042
   427  FITLD JOBNUM : 9238
   428  FITLD JOBSTART : 2002MAY25  1h55m41.05s
   429  FITLD JOBSTOP  : 2002MAY25  3h31m20.00s
   430  FITLD FILESTART : 2002MAY25  1h55m41.05s
   431  FITLD FILESTOP  : 2002MAY25  3h31m20.00s
   432  /End FITS tape header "HISTORY" information