AIPS HELP file for IMERG in 31DEC22
As of Sun Dec 4 9:28:19 2022
IMERG: Task which merges high and low res. images
High res. image
INNAME Image name (name)
INCLASS Image name (class)
INSEQ 0.0 9999.0 Image name (seq. #)
INDISK 0.0 9.0 Image disk drive #
Low res. image
IN2NAME Image name (name)
IN2CLASS Image name (class)
IN2SEQ -1.0 9999.0 Image name (seq. #)
IN2DISK 0.0 9.0 Image disk drive #
OUTNAME Image name (name)
OUTCLASS Image name (class)
OUTSEQ -1.0 9999.0 Image name (seq. #)
OUTDISK 0.0 9.0 Image disk drive #
CHANNEL 0.0 plane number from cubes
UVRANGE 0.0 Min and max baseline (klam.)
defining annulus of overlap
FACTOR 0.0 If > 0.0 , use as norm.
factor for low res. image
AVOPTION Averaging option ' ','MEAN'
DOWEIGHT -1.0 1.0 <= 0 => do not correct for
beams (BMAJ, BMIN, BPA)
BADDISK Disks to avoid for scratch.
Use: IMERG merges two input images by fourier transforming both,
normalizing the second to amplitudes within a U,V annulus of the
first, then producing an output transform plane consisting of the
inner plane from the second input, some combination of the two
within the annulus and the outer plane from the first. The output
image is the back transform of this merged U,V plane. The header
beam parameters (BMAJ, BMIN, BPA) from the two images are used to
deconvolve the beam of the second image from the second image and
to convolve the second image with the beam of the first image all
before the amplitude normalization. This reconvolution may be
suppressed with DOWEIGHT.
NOTE: This task does very little checking of the input files.
It does require that the images be the same size and that the
size be an integer power of 2 in both axes. If your images are
not a power of 2, PADIM will allow you to raise their size by
padding with zeros or SUBIM will allow you to reduce their
size. The two images should agree in all coordinates - the same
coordinate types, reference values and pixels, increments,
rotations, and so forth. OHGEO may be of use in bring the two
images into alignment. If the twop images are not aligned, very
wrong results will arise, with IMERG doing very little to
INNAME......The high res. image name. Standard defaults.
INCLASS.....The high res. image class. Standard defaults.
INSEQ.......The high res. image seq. #. 0 => highest.
INDISK......The high res. image disk drive #. 0 => any.
IN2NAME.....The low res. image name. blank => INNAME,
otherwise standard behavior.
IN2CLASS....The low res. image class. Standard behavior
except blank => 'RBEM' if INCLASS = 'RMAP'
'LBEM' if INCLASS = 'LMAP'
'IBEM' if INCLASS = anything else
IN2SEQ......The low res. image seq . #. 0 => INSEQ,
use -1 to get highest.
IN2DISK.....The low res. image disk drive #. 0 => any.
OUTNAME.....The IMERG image name. Standard defaults.
OUTCLASS....The IMERG image class. Standard behavior with
default = 'RMRG' if INCLASS = 'RMAP'
'LMRG' if INCLASS = 'LMAP'
'IMRG' if INCLASS = anything else
OUTSEQ......The IMERG image seq. #. 0 => highest unique.
If >0; image will be created if new,
overwritten if image name exists.
OUTDISK.....The IMERG disk drive no. 0 => highest with space
BLC.........Bottom left corner of IMERG image.
TRC.........Top right corner of image; both BLC and TRC
default so that the whole image is chosen.
UVRANGE.....The min. and max. baseline in klambda which define the
annular region of assumed overlap between the low and high
resolution image transforms. The normalization of the low
res. image is based on comparing mean amplitudes in this
FACTOR......The normalizing factor for the low res. image is imposed
by using FACTOR > 0.0
AVOPTION....'MEAN' means to take the average of the 2 data sets over
the full annulus. This is best if the two are in good
agreement. If they are not, then the abrupt change in
weights at UVRA(1) and UVRA(2) can cause circular
sidelobes to appear around sources. Any other value
causes a smooth change in the weight from 1.0 for the
second data at UVRA(1), to 0.5 for both at
(UVRA(1)+UVRA(2))/2, to 1.0 for the first at UVRA(2).
(A Gaussian-like function is used.)
DOWEIGHT....True means to correct the low resolution image by
deconvolving its beam and convolving the beam of the high
resolution image before setting the normalization. False
means to suppress this operation (equivalent to setting
the beam parameters to zero in both headers).
True is > 0; false is <= 0.
BADDISK.....This array contains the numbers of disks on which it is
desired that scratch files not be located. BADDISK has no
effect on input and output images.
IMERG : Task which merges high and low resolution images.
DOCUMENTOR: R.Braun NRAO/VLA
DATE OF DOCUMENTATION: 18 November 1987
RELATED PROGRAMS: VTESS,STESS,LTESS
Cornwell T.J., and Evans K.F., "A simple Maximum Entropy
deconvolution algorithm", Astronomy and Astrophysics, (1985)
Burch,S.F, Gull,S.F., and Skilling,J., "Image restoration by a
powerful Maximum Entropy method", Computer Vision, Graphics and
Image processing, 23, 113-128 (1983).