An STC "when" and "where" example

[Alasdair Allan]

Roy Williams wrote:
> Specifically I removed:
> -- Observatory location, I assume this defaults to the center of the 
> Earth.
> -- Time of observation, I assume this defaults to 1/1/2000.
> -- I changed coord_system_id="ICRS-TT-WAVELENGTH-TOPO" to be just 
> "ICRS", is that OK?
> -- Error on the position, I assume it defaults to zero error.

These are all reasonable assumptions for "generic" co-ordinates

> -- Wavelength information, please can you explain why this is in with 
> the space-time coordinate systems?

There are specialised cases where I can see it might be needed, but in 
general it did seem very off the wall to have to specify this for all 
co-ordinate instances.

> <?xml version="1.0" encoding="UTF-8"?>
> <ObsDataLocation
> xmlns="http://www.ivoa.net/xml/STC/stc-v1.20.xsd"
> xmlns:crd="http://www.ivoa.net/xml/STC/STCcoords/v1.20"
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
>
>    <ObservationLocation ID="TaxTimeEvent">
>        <crd:AstroCoords coord_system_id="ICRS">
>            <crd:Position2D unit="deg">
>                <crd:Name>RA,Dec</crd:Name>
>                <crd:Value2>148.88821 69.06529</crd:Value2>
>            </crd:Position2D>
>        </crd:AstroCoords>
>    </ObservationLocation>
> </ObsDataLocation>

This is _much_ better! It even fits in my 10 line limit...

Cheers,
Al.
-- 
Dr. A. Allan, School of Physics, University of Exeter