Include a Frame representing FITS-WCS intermediate world coordinates?
"
intermediate world coordinates"
(IWC). These Frames will have Domain name "
IWC"
for primary axis descriptions, and "
IWCa"
for secondary axis descriptions, where "
a"
is replaced by the single alternate axis
description character, as used in the FITS-WCS header. The default value for "
Iwc"
is
zero.
FITS-WCS paper 1 defines IWC as a Cartesian coordinate system with one axis for each WCS axis, and is the coordinate system produced by the rotation matrix (represented by FITS keyword PCi_j, CDi_j, etc). For instance, for a 2-D FITS-WCS header describing projected celestial longitude and latitude, the intermediate world coordinates represent offsets in degrees from the reference point within the plane of projection.