[QUAR] Re: Expressing position in RDF
seaman at noao.edu
Tue Oct 14 15:20:05 PDT 2008
I suppose I should mention the aberration of light, too...
On Oct 14, 2008, at 3:15 PM, Rob Seaman wrote:
> Hi Matthew,
>> The identifying string from the STC in the VOEvent packet is UTC-
> Point taken.
>> My goal is to represent the RA, Dec information contained in the
>> VOEvent packet in RDFa.
> Ok. Assume a simple case. Note that this cannot be called a
> "typical" case. The coordinates for a point-like target fixed on
> the celestial sphere, with negligible proper motion and parallax.
> Doppler and light travel corrections are to be dealt with downstream
> ("TOPO" + metadata for the observatory + epoch).
> How does one convey these coordinates (RA, Dec, coordsys,
> conditionally equinox)? Well, you either replicate the carefully
> negotiated truce from STC, or you make additional default
> specifications. In either case, the assumptions are implicit in the
> representation. One might, for instance, suggest something like:
> X has a SimpleWCS
> SimpleWCS has an RA (and Dec with implicit equinox and coordsys)
> My fundamental point is that for proper system engineering you avoid
> X has an RA
> because this locks you into a specific set of assumptions. Later,
> perhaps, someone will come up with a SomewhatMoreComplexWCS. In
> that case, an application can evolve to support this while retaining
> backwards compatibility for SimpleWCS.
> However it is done, there will be flavors of VOEvent packets that
> are inappropriate for representation using SimpleWCS.
>> I think the answer to my original question is that there is nothing
>> currently existing in the VO to allow me to do this succinctly.
> In that case this represents an opportunity for making an original
> contribution to the VO and to broader astronomical practice.
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