[CATALOGUE] Source Catalogue DM

[Arnold Rots]

Pedro,

I append the mapping to the STC schema, with some additional comments.
I'll be happy to answer questions.
Hope it elucidates things.

Cheers,

  - 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 head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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Source Catalog - STC Mapping
----------------------------

Following is a mapping of all elements from Pedro and Matteo's list
that are present in stc:CatalogEntryLocation.

Some preliminaries:
stc:CatalogEntryLocation was designed with the following implementation
in mind: The actual catalog data are presented as cells of a VOTable; the
stc:CatalogEntryLocation element is present in the table header and its
leafs, rather than containing actual data, are IDREFs that point to the
Field that describes the column in the table, holding the actual data.
However, there are clearly other ways of implementing things.
The element can hold multiple coordinate systems to allow, for instance,
combining equatorial and Galactic coordinates in one table; each AstroCoords
element refers to a particualr AstroCoordsSystem through an IDREF
attribute.

If distance is to be added, one may want to specify a 3-D Spherical
coordinate system with unit "deg deg Mpc", or so.  The spatial
coordinate then becomes a vector of length 3, containing RA, Dec, and
distance (or whatever spatial frame is selected).  It does allow multiple
reference frames (e.g., equatorial and Galactic).  I am assuming that
the reference position for all spatial coordinates (including distance)
is the same and most likely the barycenter - though the reference position
for redshift may be different.
Alternatively, one may want to put distance in an element with different
reference frame, like Galactic coordinates.

Proper motions are spatial velocities.  However, Doppler velocities fall
in the Redshift category.  The redshift frame in the AstroCoordSystem
specifies whether it is z or Doppler velocity, the velocity definition
used (optical, radio), and the reference origin (geocenter, barycenter,
galactic center, LSR, etc.).

I would encourage you to add errors and I have included them in the mapping.
Finally, if you use a single STC element to reference all catalog entries
you may want to consider adding an AstroCoordArea element that descibes
the volume in coordinate space covered by your catalog; I added those
mappings, too.


Mapping to stc:CatalogEntryLocation
  (not showing attributes)


coordinates (say, RA & Dec)
  CatalogEntryLocation/AstroCoords/Position2D/Value2

errors on coordinates (say, an error circle)
  CatalogEntryLocation/AstroCoords/Position2D/Error2Radius

distance
  CatalogEntryLocation/AstroCoords/Position1D/Value

error on distance
  CatalogEntryLocation/AstroCoords/Position1D/Error

proper motion (in RA and Dec)
  CatalogEntryLocation/AstroCoords/Velocity2D/Value2

errors on proper motion
  CatalogEntryLocation/AstroCoords/Velocity2D/Error2

frequency
  CatalogEntryLocation/AstroCoords/Spectral/Value

Doppler velocity
  CatalogEntryLocation/AstroCoords/Redshift/Value

error on Doppler velocity
  CatalogEntryLocation/AstroCoords/Redshift/Error

time of observation
  CatalogEntryLocation/AstroCoords/Time/TimeInstant/ISOTime
  or: CatalogEntryLocation/AstroCoords/Time/TimeInstant/JDTime

major and minor axis
  CatalogEntryLocation/AstroCoords/Position2D/Size2PA/Size

position angle
  CatalogEntryLocation/AstroCoords/Position2D/Size2PA/PosAngle

catalog coverage:
  CatalogEntryLocation/AstroCoordArea/TimeInterval
  CatalogEntryLocation/AstroCoordArea/Region
  CatalogEntryLocation/AstroCoordArea/VelInterval
  CatalogEntryLocation/AstroCoordArea/SpectralInterval
  CatalogEntryLocation/AstroCoordArea/RedshiftInterval