Expressing 2- and 3-D coordinates

[Francois Ochsenbein]

Hi Anita,

>
>We already use arrays e.g. in SIAP
><FIELD name="naxis"      ucd="VOX:Image_Naxis"           datatype="int"
>arraysize="2" />
>
>The requirements which I would see as emerging are
>1) In the above example, FITS images can have >2 axes, e.g. additional
>frequency and polarization axes (which may have only one pixel, but that
>is not the point)
>2) For the Char model, some fields can either be a single value or a range
>(e.g. spatial resolution)
>- so can an arraysize be variable?
>    * in any given VOTable? Or would it have to be set instance by
>      instance?

==> Yes, the arraysize attribute can specify variable-length

>    * In the schema, to allow the case above?

==> In VOTable, there is no validation of the data -- but tools like
    TOPcat can do this (and extremely efficiently!)

>At present, 4-axis images work fine in SIAP except that it ignors axes 3
>and 4 - but nothing 'breaks' so that's OK.
>

Cheers, francois

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Francois Ochsenbein       ------       Observatoire Astronomique de Strasbourg
   11, rue de l'Universite F-67000 STRASBOURG       Phone: +33-(0)390 24 24 29
Email: francois at astro.u-strasbg.fr   (France)         Fax: +33-(0)390 24 24 32
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