VOTable 1.4 Working Draft

[Arnold Rots]

This is about how space and time intertwine. They are not independent.
It may be more about protecting users from themselves, though - so, it
could be a strong recommendation.
The hidden complication is that the time as given in the time column does
not vary linearly at the spatial reference point.

However, one would also be left with a significant ambiguity:
Say, we have a photon detected at location S(Rs), labeled with time T(Rt),
where Rs and Rt are the reference positions.
Does T(Rt) represent the time stamp (at Rt) when the photon was detected at
S(Rs), or does it represent the time it would have been detected at Rt
(i.e., corrected for pathlength difference)? The pulsar community, for
instance, would want to know.
So, maybe this is an even stronger reason to consider requiring Rs=Rt.

  - Arnold

Arnold H Rots

Research Associate

SAO/HEAD

Center for Astrophysics | Harvard & Smithsonian

Email: arots at cfa.harvard.edu

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On Fri, Feb 15, 2019 at 4:28 AM Francois Ochsenbein <
francois.ochsenbein at gmail.com> wrote:

> Hi Arnold,
>
> I'm not sure to understand the requirement of having the same spatial
> reference position as the temporal one − measures of positions and time
> are generally un-correlated from each other in different columns of a
> table, where zero to many measures of positions / times can be reported
> in one or several coordinate / time systems; in tables reporting very
> specific events your requirement can be important, but it seems to me
> that it's out of VOTable scope...
>
> Cheers, François
>
> >on 2019-02-14 at 15:00-0500, Arnold Rots wrote:
>
> >I note that there are no restrictions imposed on the
> >timescale/reference position combination.
> >That can really set you up for major trouble.
> >And maybe one should just require that the spatial reference position
> >is the same as the temporal one. Otherwise one runs the risk of time
> >not moving linearly.
> >
> >  - Arnold
> >
>
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