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wcs - coordinate transforms
wcs [parameter=value]
wcs
is really a wrapper for AIPS worldpos/xypix WCS routines (worldpos(3NEMO)
),
much like the testpos.c routine that is publicly available, but with a more
typical NEMO command line user interface.
The following parameters
are recognized in any order if the keyword is also given:
- ref=
- The reference
coordinates (deg) at the reference pixel. Two numbers are required. These
will typically be the equivalent of the crval in fits(5NEMO)
.
- refpix=
- The
reference pixels (pixels). They can be floating point numbers and do not
have to be on or inside a ’grid’. Two numbers are required. These will typically
be the equivalent of the crpix in fits(5NEMO)
.
- inc=
- Increment at the reference
pixel. These will typically be the equivalent of the cdelt in fits(5NEMO)
.
- rot=
- Rotation angle (deg) (from N through E) at the reference pixel These
will typically be the equivalent of the crota in fits(5NEMO)
..
- type=
- Projection
type (SIN, TAN, ARC, NCP, GLS, MER, AIT). These will typically the last
4 characters in the ctype in fits(5NEMO)
.
- format=
- Output printf(3)
-style
format. [Default: %g].
- pix=
- Input Pixel number coordinates. Either one of
pix= or pos= must be given, if this one is given, conversion to world coordinates
is done. Note that pixels are 1-based in FITS, and 0-based in NEMO.
- pos=
- Input
World Coordinates. If this one is given, conversion to pixel coordinates
is done
- hms=t|f
- Determines if the first coordinate, the longitude, should
be printed in H:M:S (the default) or D:M:S format.
For a given $ra,
$dec and $fitsfile, the corresponding pixel positions are computed.
set crpix1=‘fitshead $b | grep -w ^CRPIX1 | awk ’{print $3}’‘
set crpix2=‘fitshead $b | grep -w ^CRPIX2 | awk ’{print $3}’‘
set crval1=‘fitshead $b | grep -w ^CRVAL1 | awk ’{print $3}’‘
set crval2=‘fitshead $b | grep -w ^CRVAL2 | awk ’{print $3}’‘
set cdelt1=‘fitshead $b | grep -w ^CDELT1 | awk ’{print $3}’‘
set cdelt2=‘fitshead $b | grep -w ^CDELT2 | awk ’{print $3}’‘
set pix=(‘wcs ref=$crval1,$crval2 refpix=$crpix1,$crpix2 inc=$cdelt1,$cdelt2
rot=0 type=TAN pos=$ra,$dec‘)
Here is an example how to find out what the circumscribing "box" is around
a curved RA-DEC plate in the TAN projection:
worldpos(3NEMO)
, ccdtrace(1NEMO)
, nemoinp(1NEMO)
, nemoinpx(3NEMO)
,
tabdms(1NEMO)
, impos(1MIRIAD)
, xy2sky(1WCSTOOLS)
, sky2xy(1WCSTOOLS)
src/image/wcs
- source code
Peter Teuben
14-oct-94 written PJT
2-apr-96 V1.0 man page created PJT
2-mar-03 V1.1 fixed pos->pix error; finally added to NEMO PJT
4-mar-03 V1.2 allow hms/dms conversions using nemoinpx PJT
7-may-04 V1.3 added hms= keyword PJT
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