AIPS HELP file for ALVAR in 31DEC24
As of Thu Apr 25 18:19:09 2024
ALVAR: Plots the Allan Variance of a UV data
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 #
SOURCES Source name
QUAL -10.0 Calibrator qualifier -1=>all
CALCODE Calibrator code ' '=>all
STOKES Stokes of output
TIMERANG Time range to use
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
SUBARRAY 0.0 1000.0 Sub-array, 0=>all
BIF Low IF number to do
EIF Highest IF number to do
BCHAN 0.0 First channel included
ECHAN 0.0 last channel included
ANTENNAS Antennas to include
BASELINE Baselines with ANTENNAS
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 Smoothing function. See
HELP SMOOTH for details.
SOLINT 0.0 Basic integration time in the
UV data
DOPLOT 0.0 4.0 Selects which parameter is
plotted (1-4 see help)
NPLOTS -1.0 Number of plots per page
-1 -> plot average over all
baselines
FUNCTYPE 'LG' log in Y, linear in X
'L2' log in X and in Y
DOEBAR -1.0 1.0 > 0 => plot error bars
FACTOR Scale symbols by FACTOR
SYMBOL 0.0 24.0 Plot symbol number: 1 - 24
0 -> 3 (circle)
LTYPE -410.0 410.0 Type of labeling: 1 border,
2 no ticks, 3 - 6 standard,
7 - 10 only tick labels
<0 -> no date/time
PIXRANGE PIXR(2)>PIXR(1) -> fixed
y-axis range
DOTV -1.0 1.0 > 0 Do plot on the TV, else
make a plot file
GRCHAN 0.0 8.0 Graphics channel 0 => 1.
XYRATIO 0.0 X/Y ratio 0 -> fit TV or 1 PL
BADDISK Disks to avoid for scratch
HELP SECTION
ALVAR
Task: This task computes the vector average of the included spectral
channels and IFs making a grid of data at intervals of SOLINT
in time. It then computes the Allan Variance at each possible
integration time "tau = i * SOLINT". If AV(j) is the average
at a particular tau, the Allan Variance is given by
sigma^2(tau) = < (AV(j+2) - 2AV(j+1) + AV(j))^2 > / (2 tau)
The task then plots sigma^2 as a function of tau for all
possible values of tau.
The input data must be in time order. The task is able to
handle gaps (in time) should they arise but the computation is
made more complex and less reliable by such gaps. One long
scan would really be best.
It prints the mean, rms, robust mean, and robust rms for
each baseline and IF. Spectral channels BCHAN-ECHAN are
averaged within the SOLINT and tau == SOLINT.
The display is in 2 groups of 4 columns, one row per baseline,
Stokes, and IF. The first 2 columns are the mean square Allan
variance of vector difference (IM2- 2*IM1 + IM0)**2 +
(RE2 - 2*RE1 + RE0)**2 where (RE2,IM2) is the amplitude
normalized vis at point n+2, (RE1,IM1) is the normalized vis at
n+1, etc. plus the rms of means square variance. The second
pair of columns is Allan variance in phase (PH2 - 2*PH1 +
PH0)**2 with minimization of 2 pi amibiguities. The second
group of four columns are the same, but with the mean square
variance and rms computed by robust means. Note that phases
are in radians.
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.
SOURCES....Source to be copied. ' '=> all; if any starts with a
'-' then all except ANY source named.
QUAL.......Qualifier of source to be copied. -1 => all.
CALCODE....Calibrator code of sources to copy. ' '=> all.
STOKES.....Specifies which STOKES parameters are written in the
output data set: ' ' => 'FULL'
'I','Q','U','V', 'IV', 'IQU', 'IQUV'
'RR','LL', 'RL', 'LR', 'RRLL', 'RLLR', 'RLRL'
'VV','HH', 'VH', 'HV', 'VVHH', 'VHHV', 'VHVH'
'HALF', 'CROS', and 'FULL' have sensible interpretations
depending on the Stokes present in the data. The last in
each of the 3 rows above == 'FULL'. Note that many
combinations of polarizations in the input and values
above are not supported.
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.
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
override that of FREQID. However, setting SELBAND and
SELFREQ may result in an ambiguity. In that case, the task
will request that you use FREQID.
SUBARRAY...Sub-array number to copy. 0=>all.
BIF........First IF to include. 0 -> 1.
EIF........Last IF to include. 0 -> max.
BCHAN......First channel in spectral average. 0=>all.
ECHAN......Highest channel in average. 0=>all higher than BCHAN
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 apply. <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 applied.
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.
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).
SOLINT.....Pre-averaging time in seconds. 0 -> 10.
DOPLOT.....The task computes 4 different Allan variances
(1) Mean of vector amplitude of normalized visibilities.
(2) Mean of phase adjusted to minimize 2*pi ambiguities
(3) Median of vector amplitude of normalized visibilities.
(4) Median of phase adjusted to minimize 2*pi ambiguities
DOPLOT selects which one is plotted with 0 => 3.
NPLOTS.....Number of panels per plotted page. 0 -> 2
-1 => plot the average over all included baselines
FUNCTYPE...'L2' log in both X axis (tau) and Y axis (Allan variance)
'LG' log in Y axis, linear in X axis
else linear in both
DOEBAR.....> 0 => Plot error bars (+- 1 rms)
FACTOR.....Scale plot symbols by FACTOR 0 -> 1.
If FACTOR < 0, draw lines between the points and use
abs(FACTOR) to scale the points plotted.
SYMBOL.....Choices are:
1: Plus sign 13: Star of David
2: Cross (X) 14: Seven-pointed star
3: Circle 15: Eight-pointed star
4: Box 16: Nine-pointed star
5: Triangle 17: Ten-pointed star
6: Diamond 18: 11-pointed star
7: Pentagon 19: 12-pointed star
8: Hexagon 20: 13-pointed star
9: Septagon 21: 14-pointed star
10: Octagon 22: Plus (+) with gap
11: Nine-gon 23: Cross (X) with gap
12: Five pointed star 24: Vertical line
0 -> 3
LTYPE......Labelling type, see HELP LTYPE for details:
1 = border, 2 = no ticks, 3 or 7 = standard, 4 or 8 =
relative to ref. pixel, 5 or 9 = relative to subimage
(BLC, TRC) center, 6 or 10 = pixels. 7-10 all labels
other than tick numbers and axis type are omitted.
Less than 0 is the same except that the plot file
version number and create time are omitted.
Add n * 100 to alter the metric scaling.
PIXRANGE...Plot Y axis with this range. Note that on L2 and LG this
adverb is in logarithm base 10.
DOTV.......> 0 -> use the TV; else make plot file(s)
GRCHAN.....Limit plot to one graphics channel; 0 -> use channels 1
(labels), 2 connecting line, and 4 (symbols and error
bars).
XYRATIO....X/Y plot ratio, 0 -> 1 for plot files, TV dimensions for
DOTV true.
BADDISK....The disk numbers to avoid for scratch files (sorting
tables mostly).
EXPLAIN SECTION