STC ObservationLocation

[Roy Williams]

> 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.

Roy



California Institute of Technology
626 395 3670

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