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Task: impos Purpose: Converts image coordinates between different systems. Categories: image analysis IMPOS takes a coordinate in a specified system (such as "abspix" or "arcsec") and converts it to all appropriate coordinate systems (absolute world, offset world, pixels, offset pixels). If a rest frequency is stored in the header, then in addition to the type specified in the header, spectral axes are converted to frequency (FREQ), radio velocity (VRAD), optical velocity (VOPT), redshift (ZOPT), and relativistic velocity (VELO). If the input is an image and the specified coordinate represents a valid pixel, its value is reported as well. Key: in The input image or visibility dataset. For a visibility dataset, the coordinate system is relative to the first visibility record. Key: coord Specify the coordinate for each axis that you are interested in; you don't necessarily need one for every axis in the image. No default. Key: type Specify the coordinate system of the input coordinate for each axis. Different axes can be in different systems. Choose from: "hms" HH:MM:SS.S (e.g. for RA) "dms" DD:MM:SS.S (e.g. for DEC) "arcsec" Arcseconds relative to the reference pixel "absdeg" Absolute degrees "reldeg" Degrees relative to the reference pixel "abspix" Pixels "relpix" Pixels relative to the reference pixel "absghz" GHz "relghz" GHz relative to the reference pixel "abskms" km/s "relkms" km/s relative to the reference pixel "abslin" Linear coordinate "rellin" Linear coordinate relative to the reference pixel The default for unspecified axes is the type of the previous axis. The default for the first axis is "relpix". Key: stype 'VRAD' (or 'radio'), 'VOPT' (or 'optical'), 'VELO' (or 'relativistic') - the velocity convention for a spectral coordinate. For example, the header might define a frequency axis but you could provide a velocity with "type=abskms", in which case you must qualify the velocity convention via stype, i.e. VRAD, VOPT, or VELO. Key: options Extra processing options. Several can be given, separated by commas, with minimum-match. altprj Interpret a CAR (plate carИe) projection in the input ot template image as a simple linear coordinate system with an additional 1/cos(lat0) scaling factor applied when computing the longitude, e.g. RA = (p1 - CRPIX1)*CDELT1/cos(CRVAL2). This interpretation differs significantly from the FITS standard when lat0 (i.e. CRVAL2) is non-zero. altspc Report FREQ-{HEL,LSR} axes as is, namely topocentric, i.e. don't Doppler shift to barycentric or LSRK (see help for velsw). Revision: 1.16, 2015/07/31 01:20:50 UTC