AIPS HELP file for BSGRD in 31DEC21
As of Fri Sep 17 12:39:33 2021
BSGRD: Image beam-switched data
INNAME Input UV file name (name)
INCLASS Input UV file name (class)
Last char + and - for throws
INSEQ 0.0 9999.0 Input UV file name (seq. #)
INDISK 0.0 9.0 Input UV file disk unit #
Cal. info for input:
TIMERANG Time range to include
DOCALIB -1.0 2.0 If >0 calibrate data
GAINUSE CS table to apply
FLAGVER Flag table version
STOKES Stokes' parameter to image.
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 Projection code e.g. '-SIN'
APARM 1,2,3 = RA (h,m,s)
4,5,6 = Dec (d,m,s)
IMSIZE 32. 4096. Image size (X,Y) in pixels
CELLSIZE 0.000001 4096. Cell size in arc seconds
ROTATE Correct throw angle (deg)
> 0 => in gridding
< 0 => shift gridded image
SHIFT (X,Y) image shift in asec
REWEIGHT (1) <= 0 -> interp image
= 1 -> convolved image
= 2 -> weight image
= 3 -> 1/sigma**2 image
(2) Min convolved weight
= REWEIGHT(2) *
< 0 => use abs value
XTYPE -2000. 2000. Conv. function type in x
New round types - SEE HELP
100*out + temp (see help)
YTYPE -2000. 2000. Conv. function type in y
XPARM Conv. function parms for x
YPARM Conv. function parms for y
FACTOR Correct the beam throws by
multiplying by FACTOR
ORDER Baseline order (0 or 1)
DPARM Parameters: (see HELP)
(1) scale factor plus image
over minus (0 -> 1)
(2) > 0 => apply scale before
differencing, else apply
scale with convolution
(3-4) x-pixel baseline region
1 for both images
(5-6) x-pixel baseline region
2 for both images
DOCAT -1. 1. > 0 => keep intermediate
BADDISK Disk drive #'s to avoid
Task: This task will select random position beam-switched single-dish
data in AIPS uv form in a specified field of view from two data
sets, one for the "plus" throw and one for the "minus" throw. It
makes two images, rotates the two images, removes linear
baselines from each row of the images. Then it applies a
convolution function to the difference of the two images to bring
the plus and minus images, sign corrected, into alignment.
Finally, it regrids the correc ted image into the specified
coordinate system. Calibration and flagging may be applied
during the selection process. If the requested image is too
large the program will fail. Use SDIMG for such cases followed
by OGEOM (for rotation) and BSCOR for the correction.
INNAME.....Input single-dish data file name (name).
INCLASS....Input single-dish data file name (class). The first five
characters are used. The sixth character is assumed to be
"+" for the plus throw and "-" for the minus throw (as
produced by OTFBS).
INSEQ......Input single-dish data file name (seq. #).
INDISK.....Disk drive # of input single-dish data file.
DOCALIB....If true (>0), then calibrate the data using information in
the specified CS table.
GAINUSE....Version number of the CS table to apply to the data if
DOCALIB=1. 0 = highest numbered.
FLAGVER....Specifies the version of the flagging table to be applied.
0 => highest numbered table. <0 => no flagging to be
STOKES.....Stokes' type of the desired image:
'I' => I polarization,
'Q' => Q polarization,
'U' => U polarization,
'V' => V polarization,
'RR' => right circular polarization,
'LL' => left circluar polarization,
other => 'I'
OUTNAME....Output file name (name). blank => INNAME
OUTCLASS...Output file name (class). blank => INCLASS
OUTSEQ.....Output file name (seq. #). 0 => lowest unique
OUTDISK....Disk drive # of output UV file. 0 => highest with
space for the file.
'-TAN' = tangent projection (optical),
'-SIN' = sine projection (normal interferometer),
'-ARC' = arc projection (Schmidt camera, single
'-NCP' = North celestial pole (WSRT),
'-STG' = stereographic projection,
Those below should have latitude reference value 0.0
'-AIT' = Aitoff projection, (large field)
'-GLS' = Global sinusoidal projection (large field)
'-MER' = Mercator projection (large field)
'-CAR' = Plate Carree ("cartesian'")
'-MOL' = Molweide's (large field)
'-PAR' = Parabolic (Craster - for large field)
' ' => '-SIN'
See AIPS memo nos. 27 and 46 for more detail.
APARM......1,2,3 are the RA as (h,m,s)
4,5,6 are the Dec, as (d,m,s)
The specified position is the CENTER of the RA and DEC
range before the application of the shifts (if any).
Default: uv data header RA and DEC, or, if they are 0, uv
data header Observed RA and Dec. If the data coordinates
are relative Az-El (i.e. beam switched data), then there is
no default and 0,0 would be the normal center.
If APARM(4) is -0 then use APARM(4)=-0.1.
IMSIZE.....(X,Y) image size in pixels. Must be even and between 32
CELLSIZE...(X,Y) cell size in arc seconds.
ROTATE.....Rotate the throw angle by ROTATE degrees CCW. Actually it
just shifts the two images in elevation by throw-length *
sin(ROTATE) and in azimuth by throw-length*(1-cos(ROTATE))
There are 2 methods of doing the rotation/shift:
If ROTATE > 0, the initial gridding is done shifted.
If ROTATE < 0, the gridded images are interpolated onto
Note that ROTATE = -355 is the same angle as ROTATE = 5,
but the images are done differently.
SHIFT......Probably wouldn't do what you expect: shifts the reference
pixel by -SHIFT(1)/CELL(1), -SHIFT(2)/CELLS(2). The
reference value is still set by APARM (see above).
REWEIGHT...(1) Selects the kind of output image:
<= 0 => interpolated image (convolved image
divided by a convolved image with the
data replaced by 1.0's).
= 1 => convolved image of data.
= 2 => convolved image with data replaced by 1,
i.e an image of the data weights (sum of
input data weight * uniform weight
correction * convolving function at each
= 3 => image of K/sigma**2 for an interpolated
image assuming the input weights are
K/sigma**2 for the data samples
(2) Minimum convolved weight (image with data replaced by
1.0's) to remain unblanked = REWEIGHT(2) *
< 0 => use abs(convolved weight) compared to
0 => -0.01. for interpolation output and no blanking
for convolution and weight outputs
XTYPE......Convolution function type in X-direction
1=Pillbox, 2=exponential, 3=Sinc, 4=Exp*Sinc,
= 0 or > 6 (& < 11) -> 5.
11 - 16 => circular functions in radius corresponding to
1 - 6 types above; YTYPE, YPARM are ignored.
If XTYPE < 0, then abs(xtype) is used and some of the XPARM
values are assumed to be in arc seconds rather than cells.
See HELP UV1TYPE through HELP UV6TYPE for details.
There are two convolutions, first to the + and - images and
then from the corrected az-el image to an ra-dec image.
XTYPE = 100*xtype(2) + xtype(1). Same for YTYPE.
Note that both xtype(i) have to have the same sign.
YTYPE......Convolution function type in Y-direction
XPARM......Array containing parameters for XTYPE. See HELP UVnTYPE
when n=convolution type. XPARM(5) is number samples of
convolution function used per image cell for circular
functions - 100 is used for X/Y separable functions (types
1-6). XPARM for the second gridding type is the same as
for the first if they are of the same type. Otherwise,
the second gridding uses default values for XPARM.
YPARM......Array containing parameters for YTYPE.
FACTOR.....Change the beam throws by FACTOR.
ORDER......Order of baseline removed from each row of each image.
Only 0 and 1 are allowed.
(1) The plus beam may be scaled by DPARM(1) wrt the minus
beam. (You may need to use IMFIT to determine this
ratio. Be sure to fit a baseline as well as a
Gaussian.) 0 => 1.
(2) The ratio may be applied at two different stages:
if DPARM(2) > 0, the images are scaled before they are
differenced. Otherwise, the scaling is done through a
modification of the convolution function.
(3) Start x pixel of both images to use for the first of
2 baseline regions. 0 => 1. N.B. this applies after
BLC(1) has been applied.
(4) End x pixel of both images to use for first baseline
region. 0 => all (not a good default).
N.B. above N.B.
(5) Start x pixel of both images to use for the second of
2 baseline regions. 0 => none. N.B. above N.B.
(6) End x pixel of both images to use for second baseline
region. 0 => all (an okay default).
It has been found by experimentation that it is essential
to use the same baseline regions for both images.
DOCAT......> 0 => keep the intermediate images (BSGRD+, BSGRD-,
BSROT+, BSROT-, and BSGCOR) as well as the final output
image. <= 0 => delete these asap.
BADDISK...Disk drive #'s to avoid for scratch files