[fitsbits] WCS Paper III MJD-AVG vs. DATE-AVG

[Steve Allen]

On Fri 2004-10-22T14:02:16 -0400, Doug Mink hath writ:
> 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

> 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?

The tricky part here is that this begins to tread on the grounds of a
supposed subsequent WCS paper (WCS Paper V?)  which seems likely to
have a title something like "Representations of temporal coordinates
in FITS".

The meaning of "average" in paper III is intentionally not defined.

There should presumably also be keywords akin to DATE-BEG and
DATE-END, but it is highly unlikely that these will go into paper III.
Most of all, a way of declaring the time scale being presumed for any
date-time is needed.  But given that there is a raging international
battle going on in the precision timing community, the FITS community
is not likely to agree on such things in short order.

--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
sla at ucolick.org      Voice: +1 831 459 3046     http://www.ucolick.org/~sla
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