AIPS HELP file for BPWAY in 31DEC24
As of Fri Apr 19 7:47:50 2024
BPWAY: Determines channel-dependent relative weights
INPUTS
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 #
OUTNAME Output UV file name (name)
OUTCLASS Output UV file name (class)
OUTSEQ 0.0 9999.0 Output UV file name (seq. #)
OUTDISK 0.0 9.0 Output UV file disk unit #
OPTYPE 'SORC' else 'SCAN'
SOURCES Source name
QUAL -10.0 Calibrator qualifier -1=>all
CALCODE Calibrator code ' '=>all
TIMERANG Time range to use
FREQID Freq. ID to select.
SUBARRAY 0.0 1000.0 Sub-array, 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 >0.5 correct polarization.
PDVER PD table to apply (DOPOL>0)
BLVER BL table to apply.
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0.5 apply bandpass cal.
Method used depends on value
of DOBAND (see HELP file).
BPVER Bandpass table version
SMOOTH Spectral smoothing function
Dangerous here - see help.
BIF Lower IF to include
EIF Upper IF to include
ICHANSEL Array of start and stop chan
numbers, plus a channel
increment and IF to be used
to select channels to sum to
find average spectral rms.
NORMALIZ -1.0 1.0 >= 0 -> normalize the rms
spectra
< 0 -> rms spectra are in Jy
FPARM (1) > 0 rolling T buffer to
find time rms F(1) times
(2) Normal time interval
between samples (sec)
IMPORTANT TO BE ~RIGHT
(3) Flag any visibility amp
> F(13) before time rms
0 -> 1.E6
(4) Smoothing type
(5) Smoothing width (min)
(6) Smoothing support (min)
(7) Minimum weight factor
(8) Maximum weight factor
(9) > 0 -> average Stokes
(10) > 0 ignore weights
SEE HELP
FQCENTER >= 0 -> center frequency axis
BADDISK Disks to avoid for scratch
HELP SECTION
BPWAY
Task: This task examines data, one scan at a time. In each scan, the
task finds the rms versus time for each baseline over time
intervals, which are usually fairly short, one polarization and
one spectral channel at a time. This operation is done with a
moving window to determine the rms at the center of the window.
The spectra of rmses are normalized (optionally) and then
written to a table where they are sorted, smoothed over time,
and then re-sorted to time order. These time smoothed rmses
are then used to set the weights of the data written to a new
data set. This data set is written in uncompressed form to
avoid loosing all the weights just computed.
Note that any calibration, particularly bandpass, should be
applied to the data either before or in this task.
Adverbs:
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.
OUTNAME....Output UV file name (name). Standard defaults.
OUTCLASS...Output UV file name (class). Standard defaults.
OUTSEQ.....Output UV file name (seq. #). 0 => highest.
OUTDISK....Disk drive # of output UV file. 0 => highest with space
OPTYPE.....'SORC' => do one source at a time. If > 1 source, then
data will end up out of time order.
Otherwise, do one scan at a time. The result may be
noisier but will beter reflect and real changes in the
weights and the output data will still be in time order.
SOURCES....Sources to be copied. ' '=> all; if any starts with a
'-' then all except ANY source named.
QUAL.......Qualifier of sources to be copied. -1 => all.
CALCODE....Calibrator code of sources to copy. ' '=> all.
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.
FREQID.....Frequency identifier to select (you may determine which is
applicable from the OPTYPE='SCAN' listing produced by
LISTR). This task does not use SELBAND or SELFREQ and is
easily able to accomodate all Freq IDs. <= 0 -> all
SUBARRAY...Sub-array 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.
FLAGVER....specifies the version of the flagging table to be applied.
0 => highest numbered table.
<0 => no flagging to be applied.
Keep track of your FG table versions to be certain that
you are using all of the flags that you intend to use.
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
corrected.
(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
corrected.
IMAGR uses DOBAND as the nearest integer; 0.1 is therefore
"false".
BPVER......Specifies the version of the BP table to be applied
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.
NOTE: SMOOTH IS FAIRLY DANGEROUS IN THIS CONTEXT.
Applying SMOOTH because it was applied in BPASS must
still be done. SMOOTHING after BP application will
smooth out real structure in the spectral shape of
weights. If you realy need SMOOTH to remove ringing from
narrow-band signals, run SPLAT on the data to apply the
SMOOTH and then set SMOOTH=0 for later work. 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
SMOOTH(2).
BIF........First IF included in operation
EIF........Last IF included in operation
ICHANSEL.. Array of start, stop, and increment channel numbers plus
an IF used for channel selection in the averaging to
compute a normalized rms. Up to 20 sets if channels/IF may
be entered. The first having ICHANSEL(2,i) <= 0
terminates the list. ICHANSEL(4,i) is the IF number,
with <= 0 meaning all IFs. If an IF has no ICHANSEL set
for it, then the inner 3/4 of the channels will be used.
NORMALIZ...Normally, the intent of BPWAY is to determine relative
channel weights but not to change the average weight of
each sample. NORMALIZ >= 0 does this.
NORMALIZ < 0 does no normalization so real rmses are
computed and used to write the output. Be sure in this
case to set FPARM(10) > 0.
FPARM......(1) Number of times to be included in the time rms. We
recommend an odd number and < 3 -> 3.
(2) Normal interval between samples in seconds. The
program will not do intervals longer than 2 *
FPARM(1) * FPARM(2). 0 -> 10 secs
IT IS IMPORTANT TO HAVE THIS ABOUT RIGHT. If it is
too short, in particular, then data samples that
belong in the same bin (time interval) may end up in
different bins. This happens most often when data
have been time averaged after selective flagging.
Set it to somewhat less than the averaging time -
if observations at XINT are averaged over N times,
set FPARM(2) = (N-0.5) * XINT.
(3) Examine the data before doing any other checks and
flag all samples > FPARM(3) Jy. 0 -> 1.E8.
(4) Code for type of smoothing function: 1: Boxcar,
2: Gaussian, 3: Exponential, 4: Linear, 5 Median
. 0 -> 1
(5) FWHM for Gaussian, exponential, linear in minutes.
0 -> 10
(6) Full support size for smoothing function in minutes,
the function has value 0.0 outside +- FPARM(6)/2 from
the time being evaluated. 0 -> 10 for box, median;
0 -> 3, 4, 2 * FPARM(5) for Gaussian, exponential,
and linear, resp.
(7) Minimum weight factor: the existing weight is
multiplied by 1/rms^2 so this is equivalent to
setting a maximum (normalized or not) rms. 0 -> 0.
(8) Maximum weight factor: the existing weight is
multiplied by 1/rms^2 so this is equivalent to
setting a minimum (normalized or not) rms. 0 ->
10000.
NOTE: these minimum and maximum rms are applied
before the smoothing to keep really extreme values
from affecting the smoothed values excessively.
(9) If > 0, average the rms values over polarization
before smoothing.
(10) > 1 => ignore incoming data weights in computing the
rmses and in writing the output
> 0 => set incoming weights to 1 before scaling them
on output but use them in computing the rmses
<=0 => use incoming weights throughout
**** Use > 0 or > 1 when NORMALIZ < 0. ***
FQCENTER,..> 0 => Change frequency axis reference pixel to
Nchan / 2 + 1
else => do not change reference pixel
BADDISK....The disk numbers to avoid for scratch files (sorting
tables mostly).
EXPLAIN SECTION