Agenda Changes: ImageDM discussion during Education I

[Tim Jenness]

On Jun 4, 2013, at 05:15 , François Bonnarel <francois.bonnarel at astro.unistra.fr> wrote:

> 
> 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
> 

I've always found the concept of UTYPES with WCS a bit restrictive. Ok, so they can handle simple FITS WCS but more complex WCS mappings quickly get out of control. The moves towards stackable mappings inside WCS (from STScI and Starlink) don't fit at all into the old simple FITS keyword WCS. Don't you really want the WCS UTYPE to refer to an STC-S blob?

-- 
Tim Jenness
CCAT