[TRANSFORM] What is a "frame"?

[David Berry]

Ed,

> I am not completely familiar with what is in this Frame object, but I
> have been assuming it is information on the reference frame.  In which
> case I agree.  That is not a Quantity. The reference frame information
> is metadata.  WCS, however, does provide the keywords necessary to
> describe the axis.  Those keywords are the axis Quantities, in
> algorithmic or abstract form.  The reference frame info is metadata
> within that Quantity.

I think we agree (except for differences in nomenclature) - WCS would
contain one or more Frames, each Frame describing a coordinate system in
which the position of a data value within the associated data structure
can be expressed. The WCS would also contain the Mappings (equivalent to
"algorithms"?) to enable a position in one Frame to be transformed into
any of the other Frames.

David

----------------------------------------------------------------------
Dr David S. Berry    (dsb at ast.man.ac.uk)

STARLINK project                        Centre for Astrophysics
(http://www.starlink.ac.uk/)            University of Central Lancashire
Rutherford Appleton Laboratory          PRESTON
DIDCOT                                  United Kingdom
United Kingdom                          PR1 2HE
OX11 0QX