; XTRAN ;--------------------------------------------------------------- ;! Create an image with transformed coordinates ;# TASK ASTROMETRY COORDINATES IMAGE OPTICAL ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1999-2000, 2003-2004, 2008-2009 ;; 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 ;----------------------------------------------------------------------- XTRAN LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC XTRAN: Task to create an image with transformed coodinates INNAME Input image name. blank=>any INCLASS Input name(class). blank=>any INSEQ 0.0 9999.0 Input name(seq. #). 0=>any INDISK Input disk drive #. 0=>any OUTNAME Output name(name). blank=>INNAME OUTCLASS Output name(class). blank=>INCLASS OUTSEQ 0.0 9999.0 Output name(seq. #). 0=>lowest unique OUTDISK Output image disk drive # 0 => highest with space BLC Bottom left corner of input TRC Top right corner of input ORDER 0.0 6.0 Number of parameters to fit. (Only 3 or 6 allowed) DOOUTPUT -2.0 2.0 Transform coordinates (1 => regrid image to new) (2 => copy image with fit parameters in header) INTEXT File with star positions. ---------------------------------------------------------------- XTRAN Type: Task Use: XTRAN is a generalized coordinate transformer used to find the relationship between x,y coordinates in the image and RA and Dec from user supplied standard star postiions (1000 stars maximum). If DOOUTPUT is FALSE, the transformation will be calculated, but the image header will not be updated (DOOUTPUT = -2) and no output image file will be written (DOOUTPUT=-1). If DOOUTPUT=1, a new image is created with re-gridding as needed using the transformation coefficients and filling in the appropriate parameters in the image header. If DOOUTPUT is 2, a new image is created by copying the old image with new, fitted header parameters. This is only correct for simple transformations (ORDER = 3). Note that these two transformations are not exactly the same since they do not necessarily use the same refernce pixel. WARNING: XTRAN does not do a full non-linear geometry in doing its fits. Therefore, it is limited in its accuracy and should be used only for small fields and applications not requiring high astrometric accuracy. Adverbs: INNAME......Input name of image(name). blank=>any INCLASS.....Input name of image(class). blank=>any INSEQ.......Input name of image(seq. #). 0=>any INDISK......Disk drive # of image. 0=>any OUTNAME.....Output name of image(name). blank=>INNAME OUTCLASS....Output name of image(class). blank=>INCLASS OUTSEQ......Output name of image(seq. #). 0=>lowest unique OUTDISK.....Disk drive # of Output image. 0 => highest with space. BLC.........The bottom left-hand pixel of the input image which becomes the bottom left corner of the new image. The value (0,0) means (1,1). TRC.........The top right-hand pixel of the input image which becomes the top right corner of the new image. The value (0,0) means take the top right hand corner of the image. ORDER.......Type of transformation: 3 is rotation plus x and y pixel size. ORDER=6 is rotation, x and y pixel size, plus quadradic stretch. DOOUTPUT....If = 1, a new image is created with regridding using the transformed coordinates from the xy-RA,Dec fit. If = 2, a new image is created by copying the old image and adjusting the output header parameters. This is only appropriate for an ORDER=3 fit. If = -1, compute the fit as +1 but write no output. If = -2, compute the fit as +2 but write no output. INTEXT......File name of standard star positions (8 characters). This file must have the following format: (a) The first line contains an initial guess of the RA, DEC of the center of the image (RA-hr, min,sec, DEC-deg,min,sec) in the format: 18X,F3.0,F3.0,F7.3,F3.0,F3.0,F6.2 (b) The following lines (up to 20) contain Star name, X position, Y position, RA-hr, RA-min, RA-sec, DEC-deg, DEC-min, DEC-sec in the format: A4,F7.2,F7.2,F3.0,F3.0,F7.3,F3.0,F3.0,F6.2 Note that these are fixed-length Fortran formats; the characters must appear in the columns as specified. See the example in the EXPLAIN XTRAN section. ---------------------------------------------------------------- XTRAN: Task to create an image with transformed coodinates RELATED PROGRAMS: REGRD, STRAN PURPOSE XTRAN Type: Task Use: XTRAN is a generalized coordinate transformer. XTRAN finds a coordinate relationship between image pixels and coordinates of objects located at these pixels (i.e., matching star coordinates to their pixel locations). If DOOUTPUT is FALSE, only the transformation will be calculated, but NOT applied to the image. If DOOUTPUT is 1 a new image is created regridding the input image using the transformation coefficients. If DOOUTPUT=2, the input image is copied and a corrected header is supplied. This is only correct for simple transformations. The fit to the coordinate transformation assumes the X and Y axes are perpendicular, so that the X transformation can be calculated separately from the Y transformation. The angle of orientation returned from the fit is the average of the two fits. Note that if all coordinates are in a line, a fit is not possible. (ie better fits result from stars distributed over a large area; stars in a long thin region will not produce a good fit.) In the 6-parameter case, the X and Y fits are still done individually. X distortions must be independent of Y distortions, ie an image can be compressed in one direction and stretched in another. The Name of the input file must be in the "standard" DIRECTORY:FILE format and the file name must be in UPPER CASE LETTERS. Examples: INTEXT='myarea:MYSTARS.DAT' where MYAREA is an environment variable set before starting AIPS: %setenv MYAREA /mnt/username The Input Star location file must be provided with fixed format. Example input file is listed below: 23 22 43.64 -12 23 58.0 STR1 155.98 78.75 23 22 42.23 -12 24 21.8 STR2 169.96 64.92 23 22 38.52 -12 23 23.2 STR3 159.19 67.12 23 22 41.36 -12 23 32.9 STR4 145.08 83.27 23 22 45.48 -12 24 37.8 STR5 133.07 82.89 23 22 49.19 -12 24 38.1 STR6 158.00 83.00 23 22 41.67 -12 24 37.7 AB 151.24 73.26 23 22 43.64 -12 23 58.0 Fortran formats, for those of you too young to know such things are: 18X 18 ignored characters (best left blank) A4 4 characters F7.2 7 characters, including a decimal point, blank = 0 F3.0 3 characters, if no decimal it is assumed to follow the 3 (those " 23" = "23.") The simplest thing to do is to copy the format above EXACTLY. Full lines that function as comments may be added anywhere in the file. Comment lines must begin with a dollar sign ($). ----------------------------------------------------------------