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Name

wcs - coordinate transforms

Synopsis

wcs [parameter=value]

Description

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.

Parameters

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.

Examples

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:


See Also

worldpos(3NEMO) , ccdtrace(1NEMO) , nemoinp(1NEMO) , nemoinpx(3NEMO) , tabdms(1NEMO) , impos(1MIRIAD) , xy2sky(1WCSTOOLS) , sky2xy(1WCSTOOLS)

Files

src/image/wcs     - source code

Author

Peter Teuben

Update History


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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