; IMERG ;--------------------------------------------------------------- ;! merges images of different spatial resolutions ;# Task Analysis Imaging ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1997, 2011 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- IMERG LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC 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 # Output image 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. ---------------------------------------------------------------- IMERG Type: Task 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 prevent this. Adverbs: 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 annulus. 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 VERSION: 15JAN88 PURPOSE REFERENCES 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).