Ignore spherical rotations on CAR projections?

This
attribute is a boolean value which specifies how FITS

`"`

CAR`"`

(plate carree, or
`"`

Cartesian`"`

) projections should be treated when reading a FrameSet from a
foreign encoded FITS header. If zero (the default), it is assumed that the CAR
projection conforms to the conventions described in the FITS world coordinate system
(FITS-WCS) paper II `"`

Representation of Celestial Coordinates in FITS`"`

by M.
Calabretta & E.W. Greisen. If CarLin is non-zero, then these conventions are
ignored, and it is assumed that the mapping from pixel coordinates to celestial
coordinates is a simple linear transformation (hence the attribute name `"`

CarLin`"`

).
This is appropriate for some older FITS data which claims to have a `"`

CAR`"`

projection, but which in fact do not conform to the conventions of the FITS-WCS
paper.
The FITS-WCS paper specifies that headers which include a CAR projection represent a
linear mapping from pixel coordinates to `"`

native spherical coordinates`"`

, NOT
celestial coordinates. An extra mapping is then required from native spherical to
celestial. This mapping is a 3D rotation and so the overall Mapping from pixel to
celestial coordinates is NOT linear. See the FITS-WCS papers for further details.

- Type:

All FitsChans have this
attribute.

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