wcs.ps and scs.ps

[Eric Greisen]

Both wcs.ps and scs.ps have had modifications made.  The latter was
primarily the addition of a reference on relativistic velocities
suggested by Don Wells.  wcs.ps was changed to implement the
suggestion copied below.  Remarks about the actual (deprecated) status
of CDELT were added by me.  This status means that CDELT and its
offspring may be used in writing, but only if the new forms are not
used  (i.e. CDji, PVj_m and version codes other than blank).  The
political machinations have settled on the idea that CDELT is
deprecated but will have to be understood by readers for a long time
to come.  We are recommending that, either one uses solely older forms
of coordinates or solely newer forms.  Mark and I miss the simplicity
of the CDELT formulation, but understand some of the problems
perceived by the people who opposed the CDELT * PC formulation we had
proposed.  The desire for separate spelling for primary and secondary
forms (below) is an offshoot of the change from CDELT * PC to CDj_i.

Oh well, I think we are converging.  Is there anyone who does not
think so?  See

      ftp://ftp.cv.nrao.edu/NRAO-staff/egreisen/wcs.ps
      ftp://ftp.cv.nrao.edu/NRAO-staff/egreisen/scs.ps

Thanks, 

Eric W. Greisen

--------------- Mail received from the OGIP project -------------------

Subject: Re: wcs draft
Date: Thu, 08 Apr 1999 17:40:58 -0400

Eric,

Here is a revision to the Table 7 in your wcs paper that has been
recommended by representatives of several high energy astrophysics
groups.  The main change is that instead of having 'old' and 'new'
versions of these keywords in the table, we continue to use the same
keywords as have been used in the past when no version code letter is
used, and adopt the new root names for the keywords only when the version
code letter is used.  The advantage of this is that the large body of
software that reads and writes the old keywords will continue to work in
the future in most cases (when no version letter is needed).

Sincerely,

Lorella Angelini,  HEASARC/SAX
Keith Arnaud,      HEASARC
Mike Corcoran,     HEASARC/ROSAT
Tom McGlynn,       HEASARC
Koji Mukai,        HEASARC/ASCA
William Pence,     HEASARC
Steve Snowden,     HEASARC/XMM
Jonathan McDowell, AXAF Science Center
Arnold Rots,       AXAF Science Center


- ---------------------------------------------------------------
 Keyword                Image   BINTABLE vector  Pixel List
 Description            Array   Primary 2ndary   Primary 2ndary
 --------------------------------------------------------------
 Axis Type              CTYPEjs  jCTYPn jCTYns   TCTYPn TCTYns
 Axis Units             CUNITjs  jCUNIn jCUNns   TCUNIn TCUNns
 Reference value        CRVALjs  jCRVLn jCRVns   TCRVLn TCRVns
 Reference point        CRPIXis  iCRPXn iCRPns   TCRPXk TCRPks
 Transformation matrix  CDj_is   jiCDn  jiCDns   TCDn_k TCn_ks
 Coordinate parameter   PVj_ms   jPVn_m jPn_ms   TPVn_m TPn_ms
 Coordinate increment   CDELTj   jCDLTn jCDLns   TCDLTn TCDLns


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