SIA 2.0 POS parameters

[Arnold Rots]

Let me repeat my earlier comment:
In most cases RANGE in GALACTIC can be realized by keeping a Galactic
version of all ICRS coordinates. That transformation is hardly rocket
science
and one can't argue that it constitutes a hardshipp.
See my earlier post.

  - 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 Thu, Jul 10, 2014 at 2:06 PM, Patrick Dowler <
patrick.dowler at nrc-cnrc.gc.ca> wrote:

>
> RANGE is a pain if you hav to do transformations. In the current WD, it is
> true that is is only usable if you want a coordinate range in ICRS and I
> think that generally implies searching large chunks of the sky (maybe
> methodically) because a range in ICRS doesn't correspond to any objects you
> might be studying. OTOH, a range in GAL would be useful to easily search in
> or away from the galactic plane...
>
> Previous discussions highlighted that CIRCLE is the useful search shape
> when people are studying know astronomical objects (outside solar system).
> POLYGON is the useful search shape if you are trying to find data that
> overlaps some other data you have in hand (for now, lets ignore the more
> subtle issues of amount of overlap, intersects vs contains, etc).
>
> That leaves RANGE, which in a restricted coordinate system is only really
> useful for methodical search of a large area, broken down into pieces. It
> could be almost duplicated with polygon (ignoring difference between great
> circle and line of constant latitude) except in the cases where you use
> open-ended ranges (stripe in DEC, range of RA from pole to pole)... even
> those can be done with a couple of polygons instead of one range.
>
> So, yes RANGE is a convenience shape with rather limited use and would be
> a pain to implement correctly if your DB is not in ICRS. But it is useful
> and convenient for the large fraction of the data that is in ICRS(ish)...
>
> Pat
>
> PS-Separate email on non-ICRS use to follow
>
>
> On 08/07/14 11:04 AM, Walter Landry wrote:
>
>> I have a dataset with extremely narrow rows.  Storing both coordinates
>> would increase storage by 25%.  So I store and index everything in
>> ICRS and convert as needed to GALACTIC.  Doing RANGE queries in
>> GALACTIC would be prohibitively expensive.  BOX and POLYGON queries
>> are fine.
>>
>> I guess the upshot of this is that I am starting to feel more strongly
>> that RANGE should be removed from SIA v2.
>>
>
>
> --
>
> Patrick Dowler
> Canadian Astronomy Data Centre
> National Research Council Canada
> 5071 West Saanich Road
> Victoria, BC V9E 2E7
>
> 250-363-0044 (office) 250-363-0045 (fax)
>
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