Mark Taylor wrote:
> ...
> Even if one takes the position that the correct answer in the case of
> angles is to require data providers to use decimal degrees and simply
> to ignore tables which don't do so, I think (having heard representations
> from solar physicists at least) that this doesn't solve the problem of
> times, since unlike unlike angles there is no obvious zero point.
> MJD is one convention, but there are others (e.g. JD), and there is
> currently no way within VOTable to specify which of these conventions
> you're using. The correct answer to this may be STC, but we don't
> currently have that within VOTable either. People know what is meant
> by ISO-8601 time strings. I'm not a time expert so it may be that
> this format carries subtle ambiguities as well, but from a pragmatic
> point of view it's clear that it would satisfy a need of a large
> number of potential users of the format without a major change.
You *do* need STC - I suspect no one is surprised about my saying that ;-) When you are providing a measure of an absolute time instance - whether that is through an ISO-8601 string, JD, or MJD - you still need to specify, at the very least, what timescale you are using and the location where that time instance value pertains to - unless the precision is of the order of hours, but that hardly qualifies as a general case.
>
> ...
> Mark
>
> --
> Mark Taylor Astronomical Programmer Physics, Bristol University, UK
> m.b.taylor@bris.ac.uk +44-117-928-8776 http://www.star.bris.ac.uk/~mbt/
>
Arnold H. Rots Chandra X-ray Science Center Smithsonian Astrophysical Observatory tel: +1 617 496 7701 60 Garden Street, MS 67 fax: +1 617 495 7356 Cambridge, MA 02138 arots-at-head.cfa.harvard.edu USA http://hea-www.harvard.edu/~arots/ --------------------------------------------------------------------------Received on 2006-04-28Z15:43:13