About TAPVizieR

What about TAPVIzieR?

The TAPVizieR service is available since sept-2012: it provides VizieR tables using the ADQL language and the TAP protocol.

This page lists some special points which characterize the current TAPVizieR implementation.

Query tables using ADQL

Please, refer to the help page containing dedicated examples for VizieR.

Note concerning the usage of tables and columns names:
The Tables or columns containing specials characters as "[]()." or begining with "_" or a digit need to be quoted in an ADQL query.

TAPVizieR works with the tables and columns names as they are given by the VizieR web application. The tables names (and some columns names) contains some specials characters which must be quoted.

e.g. Query the 2MASS table identified in VizieR by II/246/out.

    SELECT TOP 100 "II/246/out".RAJ200, "II/246/out".DEJ2000, "II/246/out"."2MASS" 
    FROM "II/246/out"
    

Results and storages

  • Jobs in a TAP service can be executed in synchronous or in asynchronous mode.
    • The asynchronous mode is the mode used by the VizieR TAP web interface.
    • Execute a query in synchronous mode: the TAP protocol (descriebed here) is the only way.
      (TAP URL /TAPVizieR/tap/sync , e.g.: hipparcos META)
  • Result access is limited to the owner only and is determined by the IP address.
  • Output repositories: currenly results are saved 5 days.
  • Time-out: currently, the time limit of the execution of an ADQL query is 5 hours.

Query VizieR using external softwares

Some softwares like TOPCat or TAPHandle can work with the TAP protocol and so enable to query tables coming from a remote service.
Configure these softwares with using the URL http://TAPVizieR.u-strasbg.fr/TAPVizieR/tap/.

configuring TOPcat to use TAPVizieR

Tables descriptions

The TAP tables descriptions returned only the tables informations without the columns descriptions (volumetry ~3.5Mb). Use the URL /TAPVizieR/tables/table_name to get their descriptions (e.g.: 2MASS).

The entire Schemas containing the tables and columns descriptions is available with the URL
http://tapvizier.u-strasbg.fr/TAPVizieR/tap/tables/ALLSTANDARD

The ADQL coordinate system understanding

How understand POINT(coord_syst, ra, de)?

The coordinate system parameter is not standard in the TAPVizieR service. More, it differs in function of the usage of it.
  • If it is used in the SELECT part of an ADQL query the coordinate system parameter is used in OUTPUT. So, you can use the possibility to make a change of coordinate system.
    E.g.:
    SELECT POINT('FK4', ra_icrs,de_icrs_) from c1239hip_main
  • Else the parameter is used in INPUT.
    If the coordinate system you give differs than the real coordinate system (given by the VizieR METAdata), then the TAPVizieR service will replace the parameter by the real coordinate system. In that case, the application will send Warnings.
  • In the case of a crossmatch on columns in different coordinate system, TAPVizieR will make a change of coordinate system (by default, it uses ICRS )

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