[ImageDM] Mapping

[CresitelloDittmar, Mark]

All,

The general content of Francois' summary is correct, but I have a couple
notes to add.

see below
Mark


On Fri, Dec 20, 2013 at 1:20 PM, François Bonnarel <
francois.bonnarel at astro.unistra.fr> wrote:

> In ImageDM, these attributes would be disbursed in the model.
>  e.g Mapping.SpatialAxis.CoordFrame  would be modeled at
> CoordSys.SpaceFrame.name
>        Mapping.SpatialAxis.Algorithm would be at
> CoordSys.SpaceFrame.Space2DRefFrame.projection
>        (NOTE: these are model paths, not utypes).
>
>  If Mapping is needed in siap for example, it would define the class and
> how to populate it from the disbursed ImageDM model elements.
>  (basically the reverse of what I did in this doc.)
>  The names arrangements and types can be whatever siap wants.
>
>
> My comment after  other mail exchange with Mark: We will Create a Mapping
> class in ImageDM and populate it with attributes from other classes
> (basically CoordSys. This Mapping class, closer what WCS packages are
> waiting for  could be included in SIAV2 full-metatadata    response.
>
>
ImageDM would not define Mapping.  If needed, it would be defined in SIAV2
to encapsulate the information and attach it to the 'QueryResponse' object.





>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 2nd Topic , difficulties I saw with Mapping with STC (this required a lot
> of mail exchange, so I give you my own conclusion only)
> Mark said :
>
>
> To summarize after a couple of iterations with Mark I see two difficulties
> :
>
>       A ) the Non Linear Transforms are rendered in Mark's work by STC
> "projection" attribute.  But the lookup (ans also polynomial) transforms
> have to be added. So what you are actually defining is an STC extension.
>            By the way, the SpaceFrame Mark is using do not contain a
> RefPix which is only in PixelFrame. It should be added in an extension, but
> I don't know if this makes sense.
>

Arnold, if doing a SpaceFrame -> SpaceFrame or CoordFrame -> Frame
transform.. one would need the source frame to have both the reference
"pixel" and reference "value".
STC is biased toward starting the transforms from a PixelFrame, but allows
them on SpaceFrame and CoordFrame.  I think this is good, we don't always
have a pixel system (Tables), and allows more flexibility in defining your
transitions.
  SpaceFrame may be covered by the use of its 'refPos' and 'OffsetPos"
elements.
  CoordFrame only has "RefPos" so may be lacking.



>       B ) something more conceptual:
>             I feel uncomfortable because the ("unique") CoordSys we obtain
> eventually to gather all the Mapping information MUST be :
>               a CordSys with Frame with CARTESIAN flavor not SPHERICAL
> (that means it defines coordinates in the "projected plane" )
>                It also has specific lonpole, lat pole, Ad hox referenec
> positions etc...
>             So it is not the standard , spherical Coordinate system
> belonging to the ICRS, FK5, GALACTIC ..... list that people could probably
> wait for.
>
>             -----> Hence My question : do we need a generic CoordSys
> (final spherical one) at the top lmevel of the model and another one,
> CARTESIAN, will all the transforms, seen as the "intermediate coordinate
> system" under Mapping.CoordSys ?
>
>
Do I have this right?  Is this your concern?
 + The SIAP query response has a single CoordSys in which all the metadata
is provided.
 + The Mapping object content would be independent of that.. providing the
information extracted from the ImageDM dataset.
    It has the PixelFrame/Axis definitions, the Linear transform to a
relatively undefined 'intermediate' Cartesian coordinate system
(Mapping.AxisMap),
    and the Non-Linear transform to the final WCS system, presumably all in
the standard set (IRCS, etc..)

 If there is more than this defined (Space->Space for example), then
Mapping would not accommodate those.

Remember, I am not trying to (re)define Mapping content, and there is
currently no Mapping.CoordSys in the ImageDM draft, so I am a little
confused.
Mapping would not appear in ImageDM at all, but in the SIAPV2 doc.

Mark
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