; IM2UV ;--------------------------------------------------------------- ;! converts an image to a visibility data set ;# Task Imaging UV AP ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 2005-2006, 2008 ;; 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 ;----------------------------------------------------------------------- IM2UV LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC IM2UV : Task to FFT an image and convert to a UV data file INNAME Image name (name) INCLASS Image name (class) INSEQ 0.0 9999.0 Image name (seq. #) INDISK 0.0 9.0 Image disk drive # BLC 0.0 4096.0 Bottom left corner TRC 0.0 4096.0 Top right corner OUTNAME Output uv data file name OUTCLASS Output uv data file class OUTSEQ -1.0 9999.0 Output uv data (seq. #) OUTDISK 0.0 9.0 Output drive # WTUV 0.0 Central data weight UVTAPER 0.0 UV taper in kilolambda to 30% UVRANGE 0.0 UV range in kilolambda FLUX Peak flux SHIFT Ra Dec shifts in arc sec BADDISK Disks to avoid for scratch. ---------------------------------------------------------------- IM2UV Type: Task Use: IM2UV FFTs a subportion of an image and writes the data as a uv data file. Multiple frequency channels will be handled. The output file will contain dummy values of the time and baseline random parameters. A dummy AN table will also be created. The output weights will be set to to a Gaussian function centered on the origin with the peak and widths set by the user. Note that input images must have columns at least 256 pixels long. The output file may be treated as any othe uv data set, including editing, imaging with IMAGR or MX, and concatenating with other data. Not all uv data manipulation routines will do something sensible with the output data file (e.g. calibration in CALIB). Adverbs: INNAME......The input real part name. Standard defaults. INCLASS.....The input real part class. Standard defaults. INSEQ.......The input real part seq. no. 0 => highest. INDISK......The input real part disk no. 0 => any. BLC.........Bottom left corner of the input image. 0's => whole image. TRC.........Top right corner of the input image. 0's => whole image. OUTNAME.....The output uv data file name; standard defaults. OUTCLASS....The output uv data file class; standard defaults. OUTSEQ......The output image seq. #. 0 => highest unique. Old files may NOT be overwritten. OUTDISK.....The output disk drive no. 0 => highest with space. WTUV........Weight for the data sample at u = v = 0. 0 => 1.0. UVTAPER.....Gaussian tapering applied to the weights (NOT the data) in kilo wavelengths to the 30% point. UVRANGE.....Range of spatial frequencies in 1000's of wavelengths. 0 => all. FLUX........> 0 Rescale the Fourier transform of the image to have FLUX (Jy) at the origin (u = v = 0). The scaling is done against the first spectral channel. < 0 Rescale the Fourier transform to have -FLUX at the maximum in the Fourier transform of the first spectral channel, whether or not at the origin. = 0 Use some build in scaling not much like the original visibility values that went into the image. SHIFT.......Shift the phaes from the reference position by SHIFT arc seconds in arc seconds at the referenceposition. Thus RA = RA0 + SHIFT(1)/cos(DEC) and DEC = DEC0 + SHIFT(2). 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 files. ---------------------------------------------------------------- IM2UV: Task to Fourier transform an image and convert it to a uv data format file. DOCUMENTOR: W. Cotton NRAO (preliminary) RELATED PROGRAMS: IMAGR, WTMOD, UVFLG, DBCON PURPOSE This task allows an image to be Fourier transformed and converted to a uv data format file. This allows using the tools available for editing in the Fourier domain before retransforming to the image domain using UVMAP, MX, or IMAGR. Alternately, this task allows combining data derived from a single-dish antenna with interferometer data. USAGE If the specified window in the input image is not a power of 2, then the (sub)image is zero padded to a power of two before being FFTed. The input image must have columns that are at least 256 pixels long. The coordinate projection type of the image is coded into the UU-L and VV-L fields so that the imaging routines can reconstruct the correct projection codes. Since IM2UV uses FFTs to do the transform the sampling of u-v cells is entirely determined by the image. The imaging routines assume that the u,v and w sampled scale with frequency as will always be true of an interferometer. Because IM2UV cannot sample at arbitrary u-v positions the output data can be correct for only one frequency. If more than one frequency is requested only the first will be done. The other frequencies must be processed separately. For best results when transforming the output of IM2UV back to the image plane, use twice the number of cells and half the cell spacing of the input image to IM2UV. Then use SUBIM with XINC=2; YINC=2; BLC=2,1; TRC=0 to recover the original spacing. If the retransformed image is to be deconvolved then oversampling by a factor of three or more is desirable (cell spacing 1/3 of original image) and the output image should not be subimaged until after deconvolution.