[task #15892] Search VizieR datasets that cover a certain location

[Mohammad Akhlaghi]

URL:
  <https://savannah.gnu.org/task/?15892>

                 Summary: Search VizieR datasets that cover a certain location
                 Project: GNU Astronomy Utilities
            Submitted by: makhlaghi
            Submitted on: Fri 22 Jan 2021 05:18:13 PM UTC
         Should Start On: Fri 22 Jan 2021 12:00:00 AM UTC
   Should be Finished on: Fri 22 Jan 2021 12:00:00 AM UTC
                Category: Query
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

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Details:

VizieR is a very large database, containing many datasets. But most of the
datasets only cover a portion of the sky. So when a user is interested in a
certain part of the sky, it is very helpful for them to be able to limit the
list of the datasets based on their covered position.

Doing this type of query based on the standard TAP features is not trivial.
However, Francois Ochsenbein kindly noted that it is possible with ViziR's
non-TAP interface with a command like below (for example to find catalogs
within 5 arc-minutes of the RA,Dec coordinates of 23.4621, 30.66)


curl -oout.tsv --form -c=23.4621+30.66 --form -c.rm=5
http://vizier.unistra.fr/viz-bin/asu-tsv?-meta


If we remove the '?-meta' part, all the matching rows within this  center and
radius will also be downloaded, and it is possible to download in FITS format
(when one extension per matched catalog, each extension containing the rows of
that table). However, this file can be large (because of all the data, for
example the output above is 38Mb). So we only want the meta format here.

Currently in the 'meta' mode (which is what we want in this scenario) a FITS
format output isn't supported. But the Tab Separated Value (TSV) output isn't
hard to parse automatically. So we should add this feature for queries related
to VizieR.




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