AIPS HELP file for UVIMG in 31DEC24
As of Thu Apr 18 8:09:18 2024
UVIMG: Task to grid UV data into an "image"
INPUTS
INNAME UV data (name).
INCLASS UV data (class).
INSEQ 0.0 9999.0 UV data (seq. #). 0 => high
INDISK Disk unit #. 0 => any
OUTNAME Image data (name).
OUTCLASS Image data (class).
OUTSEQ 0.0 9999.0 Image data (seq. #). 0=>high
OUTDISK Disk unit #. 0 => any
SRCNAME Source list
TIMERANG Time range to list
STOKES Stokes type to list.
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
BIF 0.0 100.0 Lowest IF number 0=1
EIF 0.0 100.0 Highest IF number
BCHAN 0.0 2048.0 Low channel number 0=>1
ECHAN 0.0 2048.0 High channel number
ANTENNAS Antennas to list
BASELINE Baselines with ANTENNAS
UVRANGE 0.0 UV range in kilolambda
SUBARRAY 0.0 1000.0 Subarray, 0=>1
Cal. info for input:
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CAL (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.
DPARM Control info:
(1) 0=amp, 1=phase, 2=rms,
3=rms/mean, 4=real part,
5=imaginary, 6=beam,
7=count, 8=1.0 if sampled
(2) 0=vec avg, 1=scalar
(3) >0 = baseline as ant pair
for B as x-axis only
(4) >0 => divide by source
IPOL flux
(5) x-axis interval: is B for
TB and is ignored, else
is the 2nd sort parameter
NO default. Units:
seconds, wavelengths
**** NO DEFAULT ****
(6) y-axis interval: T for TB
first sort parameter
**** NO DEFAULT ****
(7) > 0 => do NOT divide by
the summed weights
(8) > 0 -> use XTYPE, YTYPE
and interpolate to grid
(9) > 0 -> empty cells set
to zero, else blanked
(10) Use data weight to the
power 1/DPARM(10)
IMSIZE 1.0 18384.0 Output image size in x,y
x ignored if B
NCHAV Number of channels to include
in each plane
CHINC Increment between start
channels of each plane
SORT Desired uv image axes
DOROBUST -1.0 1.0 > 0 use ROBUST weighting
ROBUST -5.0 5.0 Brigg's robustness parameter
XTYPE 0. 20. Conv. function type in x
default spheroidal
New round types - SEE HELP
YTYPE 0. 20. Conv. function type in y
default spheroidal
XPARM Conv. function parms for x
YPARM Conv. function parms for y
SCALR3 -1. 1. > 0 => do not grid Hermitian
BADDISK Disk to avoid for scratch.
HELP SECTION
UVIMG
Type: Task
Use: Grids UV data of the selected type to form an image. UVIMG
will work on single- and multi-source files in any sort order.
It grids the data by the SORT parameters with the 2nd (faster)
parameter on the x axis and the 1st (slower) parameter on the y
axis. All samples falling into a cell are averaged by vector
or scalar averaging. Each included channel and IF may be
gridded to a separate plane of the output 3- or 4-dimensional
image. Spectral channels, but not IFs, may be "averaged"
together (where u,v,w are adjusted for each frequency before
gridding).
Note that it is usually essential to specify DPARM(5) and
DPARM(6) since an increment of 1 is normally not useful.
The task attempts to grid the data sample and its Hermitian
except when the two axes are normal baseline number (DPARM(3)
<= 0) and/or baseline length and/or time. In these three
cases, the two would land on top of each other and, at least
for phase, would be destructive. Note that both samples may
not land on the grid, as in axes X, Y, Z, and M.
DPARM(8) was added to signal your intention to use convolving
functions when interpolating to the grid. XTYPE and YTYPE are
convolve a sample potentially to multiple cells in the UVIMG
plane. Since this operation is not normally desired, the task
now requires you to set this additional adverb before it will
use XTYPE, YTYPE, XPARM, and YPARM.
Adverbs:
INNAME.....UV file name (name). Standard defaults.
INCLASS....UV file name (class). Standard defaults.
INSEQ......UV file name (seq. #). 0 => highest.
INDISK.....Disk unit #. 0 => any.
OUTNAME....Image file name (name). Standard defaults.
OUTCLASS...Image file name (class). Standard defaults.
OUTSEQ.....Image file name (seq. #). 0 => highest.
OUTDISK....Output disk unit #. Standard defaults.
SRCNAME....Source name to be gridded. Must specify if input is
a multi-source data set, otherwise all sources are
included.
TIMERANG...Time range of the data to be gridded. In order:
Start day, hour, min., sec, end day, hour, min., sec. in
days relative to reference date.
STOKES.....The desired Stokes type of the gridded data ' ' => 'I'.
Only 1 Stokes type may be used: I, Q, U, V, RR, LL, RL,
LR, VV, HH, VH, HV
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, 0=> all
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, 0=> all
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 occasionally result in an ambiguity, in which
case the task will request that you use FREQID.
BIF........Lowest IF to grid. IF will be axis 4.
**************************************************
NOTE to VLA users: IF=1 corresponds to the VLA
AC ifpairs and IF=2 corresponds to the BD ifpairs.
**************************************************
EIF........Highest IF to grid. 0 => highest.
BCHAN......First channel to grid. 0 => 1.
ECHAN......Last channel to grid. 0 => highest.
ANTENNAS...A list of the antennas to grid. If any number is
negative then all antennas listed are NOT desired and all
others are. All 0 => grid all.
BASELINE...Baselines are specified for the LIST option using
BASELINE. Eg. baselines 1-6,1-8, 2-6 and 2-8 use
ANTENNAS=1,2; BASELINE=6,8.
UVRANGE....Range of projected spacings to be gridded in 1000's of
wavelengths. 0 => 1, 1.E10
SUBARRAY...Subarray number to grid. 0=>1.
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).
MUST be false for data not in T* order.
GAINUSE....Version number of the Cal. table to apply to the data if
DOCALIB=1. Refers to a CL table for multisource data of
an SN table for single source. 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 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.
BPVER......Specifies the version of the BP table to be applied.
<0 => no BP correction.
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).
DPARM......Control info:
(1) controls the type of information to be gridded:
0 => amplitude,
1 => phase,
2 => RMS of amplitude
3 => RMS of amplitude / mean of amplitude
4 => real part of visibility
5 => imaginary part of visibility
6 => "beam" (Vis changed to 1,0)
7 => count of samples
8 => 1.0 in sampled cells
(2) controls the type of averaging:
<= 0 => vector average,
> 0 => scalar averaging (amplitude only).
(3) controls how "baseline number" is computed
<= 0 => normal baselines (1-1,1-2, 1-3, ... 1-N,
2-2,2-3, 2-4, ... 2-N, 3-3,3-4, ...)
> 0 => as antenna pair gridding each sample
twice (1-1,1-2, 1-3, ... 1-N, 2-1, 2-2, 2-3,
... 2-N, 3-1, 3-2, ... 3-N, ...)
(4) <= 0 => grid amplitudes as found in data set
> 0 => divide amplitudes by source flux
(5) x-AXIS interval: 0 -> 1 except 1.0 is forced for
B type axis. Units are wavelengths for U, V, W, X,
Y, Z, and M sort orders and seconds for T.
NO SENSIBLE DEFAULT
(6) Y-axis interval: 0 -> 1 except 1.0 is forced for
B type axis. Units are wavelengths for U, V, W, X,
Y, Z, and M sort orders and seconds for T.
NO SENSIBLE DEFAULT
(7) > 0 => do NOT divide by the count (or sum of
convolution weights) for DPARM(1) types 0
through 5. Makes image a convolution such as
done by IMAGR, UVMAP, et al.
<= 0 => do divide by the sum of counts or convolution
function weights in each cell. Makes image an
interpolation of the data.
(8) > 0 => use XTYPE, YTYPE, XPARM, and YPARM to convolve
to the grid.
<= 0 => put each sample at the nearest grid cell.
(9) > 0 => empty cells are set to 0 - if you plan to FFT
the image you must set DPARM(9) > 0.
<= 0 => emptry cells are set to magic blanks except
for DPARM(1) = 6 and 7
(10) > 0 => use data weight when gridding to the power
1/DPARM(10)
NOTE WELL: data weights are ignored if DPARM(10) is
not set!
IMSIZE.....X,Y output image size, no sensible default except for B
type axis which will be forced,
NCHAV......NCHAV is the number of channels to be averaged together
in in the gridding process. 0 => 1. If this value is
less than the total number of spectral channels, then the
output image will have multiple planes of averaged
channels. Note that all spectral planes will include
data from NCHAV input channels so the actual ECHAN used
may be less than that specified (or in the data set).
To make a single plane image from multiple IFs and
multiple spectral channels set
NCHAV >= (EIF-BIF+1) * (ECHAN-BCHAN+1)
CHINC......Number of input channels to skip between images. 0 => 1
The i'th spectral plane includes input channels
BCHAN + (i-1)*CHINC
through
MIN (ECHAN, BCHAN + (i-1)*CHINC + NCHAV - 1).
CHINC is ignored if NCHAV >= ECHAN-BCHAN+1.
SORT.......The YX axis types are specified by two keys which are
characters in the adverb SORT. The legal keys are:
B => baseline number
T => time order
U => u spatial freq. coordinate
V => v spatial freq. coordinate
W => w spatial freq. coordinate
R => baseline length.
P => baseline position angle.
X => descending ABS(u)
Y => descending ABS(v)
Z => ascending ABS(u)
M => ascending ABS(v)
Any blank character is replaced with the corresponding
character in the UV data base sort order.
For SORT='UV' to be fed to FFT, use DPARM(5) = -x
and DPARM(6) = +x (x > 0).
DOROBUST...> 0 => Do uniform -> natural weighting
If > 0, then DPARM(7) is set to 1 so that weighting is
done by this process rather than normalizing by counts
or sum of weights. Does not apply to DPARM(1) = 6 or 7.
Robust weighting is also not done for SORT='TB' with
data already sorted in TB order.
ROBUST.....Brigg's robustmess parameter. -4 uniform, 4 natural
See help file for details.
If XPARM(8) > 0, then
XTYPE......Convolution function type in X-direction
0 -> none - take nearest pixel, 1=Pillbox,
2=exponential, 3=Sinc, 4=Exp*Sinc, 5=Spheroidal,
6=Exp*BESSJ1(x)/x > 6 (& < 11) -> 5.
11 - 16 => circular functions in radius corresponding to
1 - 6 types above; YTYPE, YPARM are ignored.
See HELP UV1TYPE through HELP UV6TYPE for details.
YTYPE......Convolution function type in Y-direction
XPARM......Array containing parameters for XTYPE.
See HELP UVnTYPE when n=convolution type.
YPARM......Array containing parameters for YTYPE.
BADDISK....Disk numbers to avoid for scratch files. Scratch
files may be created by the sorting routines if
calibration or flagging is applied.
EXPLAIN SECTION