Cube/ImageDM - new diagram set.

[CresitelloDittmar, Mark]

Francois,


On Wed, Apr 30, 2014 at 1:32 PM, François Bonnarel <
francois.bonnarel at astro.unistra.fr> wrote:

>  Hi all,
>    Hummm you got more answer on you other email on datatypes than on this
> one.
>    Very nice diagrams again. The general changes for SparseData and
> NDImage seem very good to me.
>

Thanks.


>     But:
>

:(


As in my previous email at the beginning of this month, and concentrating
> on NDIMage diagram,  i still have some difficulties with association of
> AxisCoordinates with the Voxel, even after your answers of April the 4th.
>

It would probably (hopefully!) be easier to interpret with associated text,
but I suppose the more we can convey clearly with JUST diagrams, the better.



> Suppose we are building a serialization of that. Will we have a computed
> value, error for each voxel stored in the serialization ? or is the
> aggregation there to show we can potentially COMPUTE these coordinates
> values using the mapping or WCS information ?
>

This is a case where one would NOT serialize a direct translation of the
model.. too inefficient.
As a serialization, one could have 2 ND Image extensions, one for the
'value', one for the 'error'... or any number of other options.



> As for the Mapping, which is, (if I follow previous discussion embedded)
> in the AstroCoordSys, why is that one not shown on the diagram ? Why isn't
> it attached to the Pixelated data Box like PixelCoordSys ? Is it supposed
> to be adressed through the AstroAxisCoordinate ? Or is alternativly all the
> Mapping information attached to the PixelCoordSys ?
>
>
Yes.. the WCS information is distributed in the CoordSys.. via
CoordRefFrame, and stored in the PixelCoordSys.PixelFrames (transforms from
pixel -> astro).
See STC:Overview


If we relate to earlier incarnations:
  - pixelatedData == storage of ND data array.  The PixelCoordSys is
associated with this object because it contains the PixelFrame descriptions
for that array and their Transforms to the broader world coordinate
system(s).  Different data arrays may have different transforms from their
pixel coordinates to the same world coordinate systems.  The AstroCoordSys
definitions are valid for, and owned by the Dataset as a whole, so it is
associated with the ObsDataset.   It may help to show that in this diagram.

  - voxel == I am using 'voxel' to represent the fundamental ND volume of
coordinate space.  It has associated with it, the various 'coordinates' of
the volume in the ND space (pixelAxes, independentAxes), and the
'observable' value AT that location (dependentAxis).  I am not positive the
composition relation is correct here, but I think it is.
    The actual values of the AstroAxisCoordinates may be defined (generally
would be), as a transform of the pixelAxisCoordinates (via WCS info), and
computed.  This is shown in the STCMod:Coordinates diagram.
AstroAxisCoordinate is an extension of Coordinate, and has a reference to
the associated Frame which holds the Transform information needed to
compute the value. (STC: Overview)


I hope this helps.. please ask more questions!

Mark
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