[fitsbits] Start of the WCS Paper III Public Comment Period

ANNOUNCEMENT: START OF FORMAL PUBLIC COMMENT PERIOD


This is to announce the official start of the 4-week formal Public Comment
Period on the 3rd in a series of papers on FITS world coordinate systems
entitled, "Representations of spectral coordinates in FITS" written by Eric
Greisen, Mark Calabretta, Frank Valdes, and Steve Allen. This Public
Comment Period is the first step in the process of approving this paper as
part of the official FITS Standard.

This important paper describes detailed conventions for defining spectral
coordinates involving wavelength, frequency, and velocity in FITS files.
Links to the latest 04-October-2004 draft of this paper are available from
http://www.aoc.nrao.edu/~egreisen/ and the latest version also may be
obtained directly in PDF and Postscript formats at

http://www.aoc.nrao.edu/~egreisen/scs.ps (postscript)
http://www.aoc.nrao.edu/~egreisen/scs.ps.gz (gzipped postscript)
http://www.aoc.nrao.edu/~egreisen/scs.pdf (PDF)

This paper has gone through many revisions over several years, so as an aid
to readers of previous versions, the most recent changes to the document are
shown in red text and the somewhat earlier modifications made in February
2004 are shown in blue text.

Please review this paper carefully and post any comments, criticisms, or
suggestions on the sci.astro.fits newsgroup, or on the related FITSBITS
moderated mail list. (You can subscribe to FITSBITS at
http://listmgr.cv.nrao.edu/mailman/listinfo/fitsbits). If you previously
submitted comments about this paper that have not been incorporated in this
latest draft, and if you feel that they still need to be addressed, then
please submit the comments again.

There have been extensive previous discussions of this paper on the
'fitswcs' mail list at NRAO. The archive of these discussions may be viewed
at http://listmgr.cv.nrao.edu/mailman/listinfo/fitswcs.

================================================== ================
Background information on the FITS approval process

Under the "Rules and Procedures" of the IAU FITS Working Group, the first
step in the official approval process of any FITS proposal will be a formal
Public Comment Period to take place on the sci.astro.fits newsgroup
(and on the moderated FITSBITS mail list that mirrors all on-topic
postings). At the end of this public comment period the regional FITS
committees (North America, Europe, Japan, and Australia/New Zealand) will
then vote on the proposal. Following that the IAU FITS Working Group will
then conduct a final vote to approve or disapprove the proposal. These
rules and procedures are more fully described at
http://fits.gsfc.nasa.gov/iaufwg/iaufwg_rules.html.


William Pence
Chairman, IAU FITS Working Group
--
__________________________________________________ __________________
Dr. William Pence
NASA/GSFC Code 662 HEASARC +1-301-286-4599 (voice)
Greenbelt MD 20771 +1-301-286-1684 (fax)

One of the keywords introduced in this paper is MJD-AVG, representing the
average time of the observation. If MJD-AVG is absent, then DATE-OBS is used in
its place, but the latter refers to the start of the observation. Why not also
introduce a keyword DATE-AVG, with the same ISO 8601 format as DATE-OBS?

I say this mainly because I'm concerned that there is developing a split between
two different time-handling methodologies, one based on ISO 8601, and a
different methodology used within WCS, based on MJD.

William Thompson

William Thompson wrote:
One of the keywords introduced in this paper is MJD-AVG, representing the
average time of the observation. If MJD-AVG is absent, then DATE-OBS is used in
its place, but the latter refers to the start of the observation. Why not also
introduce a keyword DATE-AVG, with the same ISO 8601 format as DATE-OBS?

I second this. All of my code which deals with timing already has to deal with both
Julian Dates and ISO 8601 dates, so implementation of the more human readable
DATE-AVG would not be difficult. If both are allowed, would the standard have to
require that one take precedence over the other if both are present?

I say this mainly because I'm concerned that there is developing a split between
two different time-handling methodologies, one based on ISO 8601, and a
different methodology used within WCS, based on MJD.

It would be optimum to support both types of time specification, which is what
anyone who currently deals with time in real FITS files has to do anyway.

-Doug Mink

In article rao.edu,
William Thompson writes:
One of the keywords introduced in this paper is MJD-AVG...

Are people really using the ill-defined MJD instead of JD? I am
pretty sure the IAU recommends using only the latter. Or has the
recommendation been rescinded?

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

On Sat 2004-10-23T02:45:58 -0400, Steve Willner hath writ:
Are people really using the ill-defined MJD instead of JD? I am
pretty sure the IAU recommends using only the latter. Or has the
recommendation been rescinded?

The IAU has had a love/hate/love relationship with the MJD, see
http://www.ucolick.org/~sla/leapsecs...cales.html#MJD

Right now we are in the "love" phase.

--
Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064
Voice: +1 831 459 3046 http://www.ucolick.org/~sla
PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E 49 89 0E FE 26 B4 14 93