SIA 2.0 POS parameters

[Arnold Rots]

All of this (except the spaces) could have been taken care of by using full
STC-S strings.

  - Arnold

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Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Fri, Jun 27, 2014 at 4:24 PM, Walter Landry <wlandry at caltech.edu> wrote:

> Hello Everyone,
>
> I have been looking at the draft for SIA 2.0 and I have a few comments
> about the POS parameters.
>
> 1) POS uses spaces as semantically important elements as in
>
>      POS=Circle 10 10 1
>
>    This makes it annoying to create URL's because you must URL encode
>    the spaces as '+'.  Otherwise my web server (Apache) will strip out
>    the rest of the parameters.  If we instead used ADQL'ish syntax
>
>      POS=Circle(10,10,1)
>
>    with explicit, visible separators, that is not as prone to being
>    mangled.
>
> 2) POS has no way to specify the reference frame.  I think that should
>    be part of the spec, with the default being ICRS.  Again, straight
>    from ADQL
>
>      POS=Circle('GALACTIC_CENTER',10,10,1)
>
>    I know that some galactic people here would really like that, and I
>    recall a planetary person asking for it at the last meeting.  It
>    would also mean that I can copy and paste coordinates between ADQL
>    and SIA.
>
>    This would also make the Range geometry more useful.  There are not
>    that many things that align themselves along lat/lon lines in ICRS.
>    Though to be honest, I would be happy enough to get rid of Range.
>    Polygons and Box (see below) would cover most of the use cases.
>
> 3) Why isn't there a Point geometry?  I can specify a circle with
>    radius zero, but that is awkward and un-intuitive.
>
> 4) There should really be a Box geometry that lets you specify a
>    center, width, and height.  Otherwise, clients have to do annoying
>    math to get proper boxes near the poles.  For the queries we serve,
>    getting images covering a box is a very common operation.
>
> 5) Winding should be specified for polygons.  Making the interface too
> 'smart'
>    leads to surprising outcomes.
>
> Cheers,
> Walter Landry
>
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