roy at cacr.caltech.edu
Mon May 22 21:56:48 PDT 2006
> If you say BARY, it means you have applied a transformation. And that
> transformation is based on model assumptions.
> There are a number of applications where it is crucial that users can
> undo that transformation (the obvious one being pulsar timing).
So the obseratory location plays two semantic roles: one for TOPO
(where it is strictly necessary) and one for GEO, where it is
necessary to provide computational provenance in case of mistakes.
In that case, I suggest that other elements be mandatory. Perhaps the
time-zone where the time measurement was made? It is possible that
the time-zone conversion was not done properly -- in which case it is
equally crucial that users can undo that transformation. I for one
never know whether we are on summer time or not.
I suggest to you that in some cases the transformation from TOPO to
GEO is very simple, and in these cases it is not necessary to pass
the time-zone or the observatory location. Specifically, if the
object is distant and the error in timing of the event is much larger
than light-time across the Earth.
California Institute of Technology
626 395 3670
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