[AstroPy] Changing dimensionality of WCS

[David Berry]

On 24 September 2013 19:23, Adam Ginsburg <adam.ginsburg at colorado.edu> wrote:
> When working with data cubes, I often need to extract WCS information
> for 1 or 2 of the WCS dimensions.   The docs
> (http://docs.astropy.org/en/latest/wcs/index.html) give decent
> examples of how to generate a WCS from scratch, but I don't see any
> obvious way to extract a lower-dimensional WCS from a WCS.  Does such
> functionality exist?  If not, does it make sense to generate a WCS
> from scratch and copy over just the relevant parameters?

This is an example of the general problem - given two arbitrary
coordinate systems, one with N axes and one with M axes, is there a
transformation between them, and if so, what is it? It is addressed in
pyast by the "convert" method. If you need ideas for an API see

http://starlink.jach.hawaii.edu/docs/sun211.htx/node245.html

Implementing this sort of feature in a general way is tricky but can
be done. For simpler cases where you just want to pick a specified
subset or superset of axes from a coordinate system, pyast uses
"pickaxes". See

http://starlink.jach.hawaii.edu/docs/sun211.htx/node348.html

I know pyast is not astropy, but I point these out in case ideas are
need for how to approach these issues.

David