; AXDEFINE ;--------------------------------------------------------------- ;! Define or modify an image axis description ;# Verb Catalog ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1998, 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 ;----------------------------------------------------------------------- AXDEFINE LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC AXDEFINE: Verb to modify image axis description and values INNAME Image name(name). INCLASS Image name(class). INSEQ 0.0 9999.0 Image name(seq. #). 0=>high INDISK 0.0 9.0 Disk drive #. 0=>any NAXIS 0.0 7.0 Axis # to modify <= ndim+1 0 => ndim + 1 AXTYPE New axis type AXINC Axis increment 0 => no change AXVAL Axis value at ref. pixel = AXVAL(1) + AXVAL(2). AXREF Reference pixel location ---------------------------------------------------------------- AXDEFINE Type: Verb Use: AXDEFINE is used to add or alter axis descriptions in the catalogue map header. The last 1-point axis may also be removed from the header. Adverbs: INNAME......Image name(name). Standard defaults. INCLASS.....Image name(class). Standard defaults. INSEQ.......Image name(seq. #). 0 => highest. INDISK......Disk drive # of image. 0 => any NAXIS.......Number of the axis to be modified. If ndim+1, add a new 1-point axis as axis ndim+1. Otherwise, modify an existing axis. 0 => ndim+1. AXTYPE......Axis type (8 chars left justified). No default. Examples: 'VELO', 'FREQ', 'LAMBDA', 'TIME' To remove the last axis, set AXTYPE = ' ' and NAXIS to ndim. Only works if there is 1 point on that axis. AXINC.......Axis increment to set. 0 => no change. Units are those of AXVAL. AXVAL.......Axis coordinate value at reference pixel. Value is AXVAL(1) + AXVAL(2) in double precision. No default. Units are mks, degrees, Jy. Note: velocities are meters/sec, therefore. AXREF.......Reference pixel location. No default. ---------------------------------------------------------------- AXDEFINE: Verb to modify image axis description and values DOCUMENTOR: R. L. Brown NRAO/CV RELATED PROGRAMS: IMHEADER, MCUBE, AXTDEF, ALTSWTCH PURPOSE AXDEFINE is a general purpose utility program that allows one to define or re-define the description (or label) of an image axis. Here it is important to note that AXDEFINE is used to label an image axis; it does not in any way alter the values which comprise the image. The following are three common uses of AXDEFINE. (1) Suppose we mapped a galactic object and, in UVMAP, we rotated the map so as to present the object in galactic coor- dinates. We use AXDEFINE to label the map ordinate and abscissa as galactic longitude and latitude respectively. The appro- priate values for the new axes are entered through the para- meters AXREF, AXVAL and AXINC. (2) We are trying to build a spectral line data cube but MCUBE complains that frequency does not increment properly along what we wish to be the third axis of the cube. Use AXDEFINE to define the proper third-axis coordinate value for each image to be used in the cube. (3) We have now constructed a spectral line data cube and we want to express the third axis coordinate as velocity not frequency. Use AXDEFINE to label the third coordinate as desired. IMHEADER may be used at any time to examine the header information and axes descriptions associated with a particular image. COMMENTS NAXIS: The image abscissa is referred to as axis number 1 and the ordinate is axis number 2. Use IMHEADER when in doubt. The default value of NAXIS is to add a new axis with one point (the present image) on that axis. AXTYPE: New axis label (8 characters, left-justified). Only certain keywords are acceptable here because the program uses these words to associate physical units appropriate for that axis (e.g. one expresses 'DEC' in degrees not in, say, Janskys). Among the labels recognized in this sense are: RA. . . . .Any epoch you desire DEC. . . . Any epoch you desire GLON. . . .To designate galactic longitude GLAT. . . .To designate galactic latitude ELON. . . .Ecliptic longitude ELAT. . . .Ecliptic latitude LAMBDA. . .Wavelength (units are METERS!) FREQ. . . .Frequency (in Hz) VELO. . . .Velocity (note: in METERS/sec!!) FELO. . . .Velocity, optical convention (units: METERS/sec!!) DATE. . . .Julian date TIME. . . .Time (units are seconds) blank . . .Remove last axis. Only work if there is one point on this axis. This list is amended periodically. Check with your system manager and/or GRIPE. AXINC: The axis increment between successive points along the axis specified by NAXIS. The units are the same as those specified by AXTYPE. The increment, AXINC, may be positive or negative. AXVAL: With this parameter one specifies the value of the new axis description at a single point along the axis. That point one must, of course, also specify; this is done with AXREF. AXVAL is expressed as AXVAL(1)+AXVAL(2) so that one can enter a value with enough significant figures when necessary (especially when specifying frequency, e.g. AXVAL=1420.40E6, 5.75178E3). AXREF: Any point along the axis to be relabeled. At this point the new axis will be given the value AXVAL. AXREF wants a single number--you're specifying a point along a coordinate axis not a pixel location on a multi-dimensional image.