AIPS HELP file for SPLIT in 31DEC22
As of Sun Mar 26 9:06:34 2023
SPLIT: Task to split multi-source uv data to single source
also works on single files.
INNAME Input UV file name (name)
INCLASS Input UV file name (class)
INSEQ 0.0 9999.0 Input UV file name (seq. #)
INDISK 0.0 9.0 Input UV file disk unit #
SOURCES Source list
QUAL -1.0 Source qualifier -1=>all
CALCODE Calibrator code ' '=>all
TIMERANG Time range to copy
STOKES Stokes type to pass.
ANTENNAS Antennas to include or omit
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
BIF 0.0 100.0 Lowest IF number 0=>all
EIF 0.0 100.0 Highest IF number 0=>all
BCHAN 0.0 2048.0 Lowest channel number 0=>all
ECHAN 0.0 2048.0 Highest channel number
SUBARRAY 0.0 1000.0 Subarray, 0=>all
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL (or SN) table to apply
DOPOL -1.0 10.0 If >0 correct polarization.
PDVER PD table to apply (DOPOL>0)
BLVER BL table to apply.
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0 apply bandpass cal.
Method used depends on value
of DOBAND (see HELP file).
BPVER Bandpass table version
SMOOTH Smoothing function. See
HELP SMOOTH for details.
OUTCLASS Output UV file name (class)
OUTSEQ -1.0 9999.0 Output UV file name (seq. #)
OUTDISK 0.0 9.0 Output UV file disk unit #.
DOUVCOMP -1.0 1.0 1 (T) => compressed data
ROTMEAS Apply a rotation measure
correction - see HELP
APARM Control information:
1 = 1 => avg. freq. in IF
= 2 => avg. freq. in IF
single channel out
= 3 => avg IF's also
2 = Input avg. time (sec)
3 > 0 => Drop subarrays
4 > 0 => calibrate weights
5 = 0 pass only xc data
= 1 pass xc and ac data
= 2 pass only ac data
6 > 0 add full source name
NCHAV Number of chan. to average.
(used if APARM(1) = 1)
<= 0 -> ALL
CHINC Channel incr. between output
channels (used if APARM(1)=1)
ICHANSEL Array of channel start, stop,
and increment numbers and IF
number to be used when
averaging in frequency.
(used if APARM(1) = 2, 3)
BADDISK 0.0 9999.0 Disks to avoid for scratch
Task: Split a multi-source uv data set into single-source data files.
Multiple sources may be processed in a single run. Optionally,
calibration, editing and spectral averaging may be applied. Fully
flagged data will not be copied.
The flagging and spectral averaging functions may also be applied
to a single-source input file. SPLIT will also apply an unapplied
SN table to a single-source file. This may be done by copying an
appropriate SN table to the input file. A warning message may
appear if the SN table had previously been applied to any
SPLIT differs from SPLAT in that it cannot write a multi-source
output file and that it does not copy any calibration tables
even if they were not applied. SPLIT also offers a rotation
measure correction not available in SPLAT.
Moving sources retain their PO table information (if any).
INNAME.....Input UV file name (name). Standard defaults.
INCLASS....Input UV file name (class). Standard defaults.
INSEQ......Input UV file name (seq. #). 0 => highest.
INDISK.....Disk drive # of input UV file. 0 => any.
SOURCES....Source list. One output file will be made per source.
'*' = all; a "-" before a source name means all except ANY
QUAL.......Only sources with a source qualifier number in the SU table
matching QUAL will be used if QUAL is >= 0. If QUAL < 0,
all qualifiers will be written. These qualifiers will be
written to separate output files. Note that OUTSEQ must be
zero in this case.
CALCODE....Sources may be selected on the basis of the calibrator code
given in the SU table.
' ' => any calibrator code selected
'* ' => any non blank code (cal. only)
'-CAL' => blank codes only (no calibrators)
anything else = calibrator code to select.
NB: The CALCODE test is applied in addition to the other
tests, i.e. SOURCS and QUAL, in the selection of sources to
TIMERANG...Time range of the data to be copied. In order:
Start day, hour, min. sec,
end day, hour, min. sec. Days relative to ref. date.
STOKES.....The desired Stokes type of the output data:
'LR','HALF' (=RR,LL), 'FULL' (=RR,LL,RL,LR)
ANTENNAS...A list of the antennas to include in the output data set.
If any number is negative then all antennas listed are
NOT to be included.
SELBAND....Bandwidth of data to be selected. If more than one IF is
present SELBAND is the width of the first IF required.
Units = kHz. For data which contain multiple
bandwidths/frequencies the task will insist that some form
of selection be made by frequency or bandwidth.
SELFREQ....Frequency of data to be selected. If more than one IF is
present SELFREQ is the frequency of the first IF required.
Units = MHz.
FREQID.....Frequency identifier to select (you may determine which is
applicable from the OPTYPE='SCAN' listing produced by
LISTR). If either SELBAND or SELFREQ are set, their values
overide that of FREQID. However, setting SELBAND and
SELFREQ may result in an ambiguity. In that case, the task
will request that you use FREQID.
BIF........First IF to copy. 0=>all.
EIF........Highest IF to copy. 0=>all higher than BIF
BCHAN......First channel to copy. 0=>all.
ECHAN......Highest channel to copy. 0=>all higher than BCHAN
If APARM(1) = 1, the actual # of output channels will be
(BCHAN-ECHAN+1-NCHAV)/CHINC + 1
Thus, ECHAN is the highest channel in the input averaged
into the output and is the highest output channel only if
NCHAV and CHINC are 1.
SUBARRAY...Subarray number to copy. 0=>all.
DOCALIB....If true (>0), calibrate the data using information in the
specified Cal (CL) table for multi-source or SN table for
single-source data. Also calibrate the weights unless
DOCALIB > 99 (use this for old non-physical weights).
GAINUSE....Version number of the CL table to apply to multi-source
files or the SN table for single-source files.
0 => highest.
DOPOL......If > 0 then correct data for instrumental polarization as
represented in the AN or PD table. This correction is
only useful if PCAL has been run or feed polarization
parameters have been otherwise obtained. See HELP DOPOL
for available correction modes: 1 is normal, 2 and 3 are
for VLBI. 1-3 use a PD table if available; 6, 7, 8 are
the same but use the AN (continuum solution) even if a PD
table is present.
PDVER......PD table to apply if PCAL was run with SPECTRAL true and
0 < DOPOL < 6. <= 0 => highest.
BLVER......Version number of the baseline based calibration (BL) table
to appply. <0 => apply no BL table, 0 => highest.
FLAGVER....specifies the version of the flagging table to be applied.
0 => highest numbered table. <0 => no flagging to be
DOBAND.....If true (>0) then correct the data for the shape of the
antenna bandpasses using the BP table specified by BPVER.
The correction has five modes:
(a) if DOBAND=1 all entries for an antenna in the table
are averaged together before correcting the data.
(b) if DOBAND=2 the entry nearest in time (including
solution weights) is used to correct the data.
(c) if DOBAND=3 the table entries are interpolated in
time (using solution weights) and the data are then
(d) if DOBAND=4 the entry nearest in time (ignoring
solution weights) is used to correct the data.
(e) if DOBAND=5 the table entries are interpolated in
time (ignoring solution weights) and the data are then
BPVER......Specifies the version of the BP table to be applied if
DOBAND > 0. 0 => highest numbered table.
<0 => no bandpass correction to be applied.
SMOOTH.....Specifies the type of spectral smoothing to be applied to
a uv database . The default is not to apply any smoothing.
The elements of SMOOTH are as follows:
SMOOTH(1) = type of smoothing to apply: 0 => no smoothing
To smooth before applying bandpass calibration
1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc
To smooth after applying bandpass calibration
5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc
SMOOTH(2) = the "diameter" of the function, i.e. width
between first nulls of Hanning triangle and sinc
function, FWHM of Gaussian, width of Boxcar. Defaults
(if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) =
1 - 4 and 5 - 8, resp.
SMOOTH(3) = the diameter over which the convolving
function has value - in channels. Defaults: 1,3,1,4
times SMOOTH(2) used when input SMOOTH(3) < net
OUTCLASS...Output UV file name (class). Standard defaults.
The output file name will be the first 12 characters of the
name of the source. If more than one "source" has the
same name, the affected output file names have the
CALCODE and QUAL inserted in characters 9-12.
For single-source files, the output name will be INNAME.
OUTSEQ.....Output UV file name (seq. #). 0 => highest unique
If QUAL = -1, OUTSEQ must be zero if there are in fact more
than one qualifier for a given source name.
OUTDISK....Disk drive # of output UV file. 0 => highest with space for
DOUVCOMP...If true (DOUVCOMP > 0) the output data is written in
compressed format which can result in a substantial
reduction in disk space needed. DO NOT USE THIS OPTION if
there is channel-dependent flagging and and you are doing
spectral averaging (APARM(1) > 0). If there is
IF-dependent flagging and you are using IF averaging
(APARM(1) > 2.5) this option is also not recommended.
ROTMEAS....Not 0 => apply a rotation measure correction to the
output Q and U Stokes. This can either be done in a
STOKES='IQUV' output form or an RR/LL/RL/LR form.
Qout = Uin sin(2D) + Qin cos(2D)
Uout = Uin cos(2D) - Qin sin(2D)
RLout = RLin (cos(2D) - j sin(2D))
LRout = LRin (cos(2D) + j sin(2D))
where j = sqrt(-1) and D = ROTMEAS * Lambda^2.
(1) If 0 < APARM(1) <= 1.5, then a boxcar spectral
smoothing is applied to the spectra after calibration
and before output under control of NCHAV and CHINC.
If APARM(1) > 1.5, then all frequency channels in
each IF (under control of ICHANSEL) will be averaged
in the output. If APARM(1) > 2.5, then all IF's will
be averaged also, providing a one pass process for
spectral averaging of calibrated VLBI data.
WARNING: the output frequency will be corrected to
the averaged frequency as will the values of u,v,w,
but any IF-dependent editing will make this
correction less than accurate. Also the output data
are computed by a weighted average while the
frequency is a straight average. If weights vary
significantly between IFs (and they often do) then
the corrections to u,v,w will not have been correct
and the error will be sample dependent.
(2) If phase rate corrections are to be done as part of the
calibration, then the integration time of the input
data must be given in APARM(2) to allow for an
amplitude correction to correct for the effect of time
smearing on the data. Default is no correction. There
is no time averaging of the output data.
(3) If APARM(3) > 0 then drop the subarray code from the
(5) If APARM(5) = 0 then SPLIT will pass only cross-power
data, this is the default mode. If APARM(5)=1 then both
cross-power and total-power data will be passed; if
APARM(5)=2 then only total-power data will be passed.
(6) If APARM(6) > 0, the full 16 character source name is
added to the header. The first 8 characters in keyword
SOURNAM1, the second 8 in keyword SOURNAM2.
NCHAV......If APARM(1) = 1, the number of channels to be averaged
together in each output channel. 0 => ALL. If this value
is less than the total number of channels, then a
multi-channel data set will result.
CHINC......If APARM(1) = 1, the number of input channels to skip
between output channels. 0 => NCHAVG
This may be used to separate the output channels in
frequency or to have them overlap. The most common usage
is to have CHINC = NCHAV.
ICHANSEL...The channels to be averaged when APARM(1) > 1.5 in the
form of an array of start and stop channels plus a
channel increment and the IF to which they apply. All 0
=> BCHAN, ECHAN, 1, 0. ICHANSEL(4,i) gives the IF and 0
means all IFs. Up to 20 groups of these 4 numbers may be
specified. Note that the channel numbers are absolute
numbers; they are NOT relative to BIF and BCHAN.
For instance if your data had a spectral line covering
channels 56 - 80, and you wished to exclude channels 1 -
10 and 121 - 128 because of bandpass effects, then you
could set APARM(1) = 2, and ICHANSEL = 11, 55, 1, 0, 81,
121, 1, 0 for a 1-IF data set. If you only wished to use
every other channel from the second group then you would
set ICHANSEL = 11, 55, 0, 0, 81, 121, 2, 0.
BADDISK....A list of disks on which scratch files are not to be
placed. This will not affect the output file.