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Basic Information on uvedit


Task: uvedit
Purpose: Editing of the baseline of a UV data set.
Categories: calibration, uv-data

UVEDIT is a MIRIAD task which allows baseline editing of a UV
data set.  As a result of the editing, certain header variables
of the data set are changed.  The headers `corr' and `wcorr'
are always changed since they are the data themselves.  The
headers `coord(2)' are the baseline coordinates and, as a
result, are also always changed (except with the option nouv).
The UV variable headers `lst', `ut', and `time' are updated
whenever a time offset is entered.  The headers `ra', `dec',
`obsra', and `obsdec' are changed whenever a positional
correction is entered with the ra or dec input.  Finally,
antenna coordinate corrections will cause the header `antpos'
to be corrected.

NOTE: There can be NO select keyword for this routine!  If
one includes the select option, then data that is not selected
will not be copied!

Key: vis
The name of the input UV data set.  At least one file name must
be supplied.  Up to 50 visibility files are currently allowed.

Key: source
The name of the source to apply corrections to if more than
one source is present in a UV data set.  All UV data that does
not correspond to the input source name is copied without being
edited.  If this keyword is not set (the default), then all
sources are edited.  Only one source name may be input.
Note: it probably doesn't make sense to use this keyword with
any other options except the ra and dec keywords.  If any other
editing (except ra/dec) is requested along with this keyword,
a warning message will be issued but the editing will proceed.

Key: apfile
The name of a file that contains the absolute antenna positions
entered in increasing antenna order.  Only one antenna position
file is permitted.  The first line of the file is ALWAYS skipped
and the remaining lines MUST contain three entries corresponding
to the X, Y, and Z equatorial coordinates, respectively, in units
of nanoseconds.  The function of this keyword is identical to the
``antpos'' keyword except that there is no way to specify a
subset of antennae; every antenna up to and including the largest
antenna number must be present in the file.
NOTE: You may only specify at most one of the ``apfile'',
      ``antpos'', or ``dantpos'' keywords.

In the case of options=sma, the apfile is the original
antenna file which can be copied over from the original
MIR-formated data, e.g. 050604_03:44:03/antennas which
contains four entries corresponding to the antenna number, 
the X, Y, Z geocentric cooridnates in unit of meter.
the reference antenna's X,Y,Z coordinates are specified 
to be zeros. Any corrections for the antenna positions 
must be given in the keyword smaoffset below. If no entries
are input from the keyword smaoffset, positions in the ``apfile''
are considered as the updated values and will be used to 
correct for the vis data. 

Key: smaoffset
Inputs are the antenna coordinate offsets for SMA entered in
the following order (NO checking is done for consistency):
     smaoffset = A1,X1,Y1,Z1,A2,X2,Y2,Z2,A3,X3,Y3,Z3,....
The input values are the antenna number and the three geocentric
coordinate offsets (entered in units of millimeter). These input
values are added to the original absolute coordinates read from 
the antenna file given in keywork apfile.

Note that A1 does not necesarily have to correspond to Antenna 1;
it is used to represent the variable containing the antenna
number.  Antennas present in the data but not included in the
input value list are treated as having a zero coordinate offset.

Key: antpos
Inputs are the absolute equatorial coordinates entered in the
following order (NO checking is done for consistency):
     antpos = A1,X1,Y1,Z1,A2,X2,Y2,Z2,A3,X3,Y3,Z3,....
The input values are the antenna number and the three equatorial
coordinates (entered in units of nanoseconds).  Note that A1 does
not necesarily have to correspond to Antenna 1; it is used to 
represent the variable containing the antenna number.  Antenna
(and the corresponding coordinates) not included in the input
listing do not have their coordinates changed.
NOTE: An antenna position value of zero is not possible.  If
an antenna value is set to zero, the current value from the
data is used.  To force an antenna position value to be zero,
use the keyword ``dantpos''.
NOTE: You may only specify at most one of the ``apfile'',
      ``antpos'', or ``dantpos'' keywords.

Key: dantpos
Inputs are the equatorial coordinate offsets entered in the
following order (NO checking is done for consistency):
     dantpos = A1,X1,Y1,Z1,A2,X2,Y2,Z2,A3,X3,Y3,Z3,....
The input values are the antenna number and the three equatorial
coordinate offsets (entered in units of nanoseconds).  These input
values are added to the absolute coordinates read from the data.
Note that A1 does not necesarily have to correspond to Antenna 1;
it is used to represent the variable containing the antenna
number.  Antenna present in the data but not included in the
input value list are treated as having a zero coordinate offset.
NOTE: You may only specify at most one of the ``apfile'',
      ``antpos'', or ``dantpos'' keywords.
NOTE: The dantpos keyword is the usually used when correcting antenna
position errors in a VLA observation. The  coordinate system used by
Miriad and the VLA are the same, and the baseline changes provided
by the VLAIS system need only be changed from units of meters to nanosec
when using uvedit (1 nanosec = 0.2997 meters).

Key: ra
Input is either an absolute or delta right ascension of the
phase tracking center.  If one value is present, it is considered
as a offset position and is to be entered as time seconds.
Otherwise, three values are expected and are to be entered in
the following order:
     ra = HH,MM,SS.S
The right ascension (offset) is relative to the epoch coordinates.
The default value is 0 seconds offset (no change).

Key: dec
Input is either an absolute or delta declination of the phase
tracking center.  If only one value is present, it is considered
as a offset position and is to be entered in arcseconds.
Otherwise, three values are expected and are to be entered in
the following order:
     dec = DD,MM,SS.S
The declination (offset) is relative to the epoch coordinates.
The default value is 0 arcseconds offset (no change).  If the
absolute declination is negative but the DD value is 0, then make
the MM value negative.  If MM is also 0, then make SS.S negative.

Key: time
Input is a time offset (in seconds) to be added to the clock time.
The default value is 0 seconds offset (no change).

Key: delay
Inputs are the delay error corrections for each antenna.
The inputs are the delay values for each antenna entered in the
following order (in units of nanoseconds):
     delay = D1,D2,D3,....
If no value for delay is specified, the array of antenna values
are set to 0 nanoseconds offset.  Also, a resulting difference
(D[i]-D[j]) of less than 0.05 nanoseconds is ignored (no change).
If a difference exists, the digital wide band data will be
reconstructed.  All previously flagged narrow band data will
be ignored in the reconstruction.  Also, the two (2) end
channels of each window will be ignored in the reconstruction.

Key: out
The name of the output visibility file.  This parameter is
ignored when more than one visibility file is given.  If no value
for ``out'' is given or more than one visibility file is input,
then the output file name(s) will be the same as the input file
name(s) but with an "_c" appended to the file name
(ie. "Vis = saturn,jupiter" will result in output files "saturn_c"
and "jupiter_c").

Key: options
Task enrichment options.  Minimum match is active.
  nouv     Do not recompute the uvw (coord(1..3)
           This option should, in principle, only be used with 
           the delay correction; 
           all other corrections should recompute u,v and w
  dra
           Multiply the dra values by a cos(obsdec) correction.
           This is used to correct the dra value in the uv
           dataset for MINT data taken at Hat Creek before
           11dec93.  Before that date, the 1/cos(obsdec)
           correction was not applied to the dra in the grid
           file, so that the pointing was incorrect (instead
           of dra arcseconds offsets, the offsets were
           dra*cos(obsdec) arcseconds).
           NOTE:  The obsdec used is the "old" obsdec.  If there
           is a correction in declination, this is NOT applied
           in computing the cos(obsdec).
  sma
           Allows to use the SMA corrdinates system, i.e.
           The geocentric coodinates in unit of meter
  uvrotate Rotate uv-coordinates from current to standard epoch.
           This is needed for BIMA data, or any data that keeps
           their UV(W) in current epoch instead of the more common
           standard epoch.
  time     adjust the time to the start of an integration time, 
           instead of the middle. Hence an offset of -inttime/2 will be 
           applied. Unlike the TIME keyword described above, this will have
           no other side effect. After this change 'ut' and 'time' should
           agree again as they did erroneously in BIMA data and CARMA
           data before Feb 2006.
           Normally 'ut' and 'time' are the mid point of each integration.
           Do not use this option unless you know what you are doing.

User Guide References to uvedit

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Generated by smamiriad@cfa.harvard.edu on 09 Jul 2012