[ImageDM] Mapping

[CresitelloDittmar, Mark]

Francois,

Can I ask for some clarification?


On Fri, Dec 13, 2013 at 12:35 PM, François Bonnarel <
francois.bonnarel at astro.unistra.fr> wrote:

> Hi all,
>     Sorry for the typos. Hope I fixed them now
>
>    after reading Mark's document I will have a few comments on the final
> step (but I went through all the steps before)
>
>      - Information needed for Mapping transformation is dispersed in
> several different objects. I think Mark himself pointed that "limitation"
>

To clarify on my side..
I feel the Mapping object consolidates a lot of information which IS
dispersed in the model.  The description of the attributes and their role
show that.  I have just formalized the distribution into STC objects.
And again.. if there is a need for an 'encapsulation' of this information
for a QueryResponse or something, that is fine.  I just think the data
product model (ImageDM) should have the distribution formalized.



>      - The Axis Frames and Pixel FRAMES are customized frames (basically
> because they imply reference  Positions) They are not the natives
> Coordinate systems you could associate "a priori" to the datasets. We
> probably need different Coordinate systems elsewhere in the ImageDM
>

In the very last diagram, I left off the CoordSys and PixelCoordSys nodes
which are in figures 3 and 4.  My thinking is that ALL coordinate systems
would be kept together as (1..*) CoordSys hanging off the main object
(Image) and each Axis would have a reference to the relevant Frame within a
CoordSys.

I don't understand what you mean about the 'customized' frames here.  All
of the frames in the last picture are STC Frame descriptions.
The PixelFrame holds a reference to a "SpaceRefFrame" (for example) which
has the Transform between the SpaceFrame and PixelFrame.
The PixelFrame also has the reference pixel and position.



>      - The current STC projections (as Mark said also) is limited to
> trigonometric projections and  doens't allow something like lookup tables
> and even not polynomial transformations such as the one required for
> Schmidt plates or some other wide field images. So If we use STC for
> storing mapping information we need to EXTEND STC first to these kind of
> "projections".
>
>
I'm not sure it is in the STC domain to define all the possible
transforms.  I'd much rather work the problem at that level than try to
re-create the whole coordinate system dependency model.

Thanks for the input!
Mark
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