Agenda Changes: ImageDM discussion during Education I

[François Bonnarel]

Hi Arnold,Hi everybody,
Le 17/05/2013 09:46, Rots, Arnold a écrit :
> Since that session was not really completed (or, if it did,
> I wasn't able to find out where and when), I posted some
> comments on the DM sessions Twiki page, in the form of
> some slides regarding the implementation of WCS in STC.
> You may recall that Francois asserted that there was no
> such support.
This is not true. I said it could be difficult or heavy in the first DAL 
session. But I didn't say there was no support. In the small Image DM 
session I presented slides (there are on the DM Heidelberg session page) 
where I proposed STC  utypes for the ref pos and the CDmatrix and 
projection. I identified Cart2DRefFrame as the package to do that. And I 
also identified PixelCoordSystem as the package able to describe the 
Reference pixel (CRPIX). I didn't notice your slides at that moment, 
sorry.  Below I discuss your example in term of ImageDM utypes (path 
utypes) to be used in DAL services query responses.
> There is; see: table 4, Appendix A, and the
> example in Appendix B.2.
> The main issue is that STC data model was designed to provide a
> characterization of the data it referred to along its coordinates.
> Part of that was the WCS projection.
> When the characterization role is rejected and one starts
> cherry-picking pieces from the data model, it becomes more
> difficult to put the WCS information back in, since the integrity
> of the data model has been lost.
> To be blunt: the WCS support is there, but the way you choose
> to use STC may make it very difficult to take advantage of it.
If we think to provide WCS (or Mapping) for an image along the lines of 
the example in your slides what would be the utypes ?
I found those with their equivalent WCS FITS Keywords
PixelCoordSystem.PixelCoordFrame.Cart2DrefFrame.projection ---> second 
part of CTYPE
PixelCoordSystem.PixelCoordFrame.Cart2DrefFrame.Transform2 ----> "CDELT" 
keywords
PixelCoordSystem.PixelCoordFrame.CoordRefPos.Vector2DCoordinate ----> 
"CRVAL" Keywords
PixelCoordSystem.PixelCoordFrame.CARTESIAN.naxes ----> NAXES
PixelCoordSystem.PixelCoordFrame.ReferencePixel.Pixel2D.Name1 ----> 
First part of CTYPE1
PixelCoordSystem.PixelCoordFrame.ReferencePixel.Pixel2D.Name2 -----> 
First part of CTYPE2
PixelCoordSystem.PixelCoordFrame.ReferencePixel.Pixel2D.Value2  ------> 
CRPIX Keywords

Of course this works. The STC/WCS solution I had in mind was a little 
different because WCS is actually at least a two step transformation
     Sphere ------> projected plane (Wolrld coordinates to "standard" 
coordinates)
     projected plane ----> pixel plane
I thought the first transformation is best rendered SEMANTICALLY by a 
real AstroCoordSystem with a Custom Cart2DSpaceRefFrame and a Custom 
RefPos. These features do not really belong to Pixel space in my sense.
Then the second transformation (using the matrix/CDELT Transform2 and 
Pixel reference position) could be rendered by the PixelCoordinateSystem

Alternatively I also proposed the Mapping stuff as it is done in the 
ImageDM draft. Something much closer the organisation of WCS keywords like

Mapping.CoordRefPixel
Mapping.CDmatrix
Mapping.Projection
etc...


I presented these two alternatives for an open discussion. But you were 
in another room !!!

Best regards
François
>
> Cheers,
>
>   - Arnold
>
>
> On Mon, May 13, 2013 at 1:24 PM, Jesus Salgado 
> <jsalgado at sciops.esa.int <mailto:jsalgado at sciops.esa.int>> wrote:
>
>     Dear all,
>
>     Massimo Ramella has kindly provided part of the time of his
>     Education 1 session on
>     Thursday 11:00–12:30 to finish the discussion on ImageDM draft
>     that we were having
>     during DM1 session.
>
>     That means, we will have F. Bonnarel presentation that could not
>     give today plus
>     the brainstorming.
>
>     Please take note of that :)
>     Cheers,
>     Jesus
>
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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 <mailto:arots at cfa.harvard.edu>
> USA http://hea-www.harvard.edu/~arots/ 
> <http://hea-www.harvard.edu/%7Earots/>
> --------------------------------------------------------------------------------------------------------------
>


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