New release of WCS draft

[Jeff Bloch]

The version I pulled is dated 9.9.1996 and appears to have differences 
from previous versions.

However, there is something that I would like to see expanded. I restate a
plea that I made many months ago. I would like to see more EXPLICIT language
in the description of the CSC, QSC, and TSC on how to treat the existence or
non-existence of the CUBEFACE axis type. 

As we understand and use Eric's wcslib software package, it is possible to
lay out the whole sky in the "lazy T" configuration in a single plane of the
FITS image, not use the CUBEFACE axis type keyword, and the reference pixel
will be located at the center of face "1". However, at any valid location on
the map, a value for "CUBEFACE" is implied. It is also possible, for
compatibility with the COBE convention, to store the six planes of the
projection as a data cube with the third axis having the type CUBEFACE. 

This arrangement is sort of implied in the document, but I am afraid that 
authors of new software implementing these conventions may not fully 
appreciate the two ways of dealing with these projections from the 
description.

Here is an in-use example header for a map that does not use the CUBEFACE 
axis type:

SIMPLE  =                    T / Written by IDL:  11-Sep-1996 07:27:32.00
BITPIX  =                   32 /
NAXIS   =                    2 /
NAXIS1  =                 1440 /
NAXIS2  =                 1080 /
DATE    = '11/09/96'           / Creation date (DD/MM/YY) of FITS header
CTYPE1  = 'RA---QSC'           /COORDINATE TYPE
CTYPE2  = 'DEC--QSC'           /COORDINATE TYPE
EQUINOX =            1996.6948 /ALEXIS MAPS ARE IN CURRENT EPOCH
CD001001=            1.0000000 /DEGREES/PIXEL
CD002001=            0.0000000 /DEGREES/PIXEL
CD001002=            0.0000000 /DEGREES/PIXEL
CD002002=            1.0000000 /DEGREES/PIXEL
CDELT1  =          -0.25000000 /
CDELT2  =           0.25000000 /
CRPIX1  =              1260.50 /REFERENCE PIXEL IN X
CRPIX2  =              540.500 /REFERENCE PIXEL IN Y
CRVAL1  =            0.0000000 /R.A. (DEGREES)
CRVAL2  =            0.0000000 /DEC  (DEGREES)
LONGPOLE=              180.000 /LONGITUDE OF POLE (DEGREES)


I have placed the complete map as a gziped file called 
"sample_wcs_qsc.fits.gz" at our anonymous ftp site:

nis-ftp.lanl.gov

in directory "incoming".

						Jeff


On Fri, 13 Sep 1996, Peter Bunclark wrote:

> Eric Greisen wrote:
> > 
> >      This broadcast is to announce a new version of the paper
> > describing the coordinates proposal by Mark Calabretta and myself.
> > The paper is available as wcs.all.ps, wcs.all.ps.Z and wcs.none.ps.Z
> > (only) from the fits ftp/WWW site (fits.cv.nrao.edu) in the
> > fits/documents/wcs directory.
> > 
> > 
> 
> I just pulled and printed it - it looks exactly the same as the document that has been there
> many months - dated 30.10.1995...
> 
> Pete.
> 
> 

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Jeffrey Bloch					Office:    (505) 665-2568
Astrophysics and Radiation Measurements Group	ALEXIS SOC:(505) 665-5975
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