When writing a FrameSetFrameSet in which the WCS
FrameFrame is a SkyFrameSkyFrame to a
FitsChanFitsChan, success depends on the following conditions
being met:
- The MappingMapping from pixel coordinates (the base Frame
in the FrameSet) to the WCS SkyFrame includes a WcsMapWcsMap.
- The Mapping prior to the WcsMap (i.e. from pixel to IWC) is linear.
- The Mapping after the WcsMap (i.e. from native spherical to
celestial coordinates) is a spherical rotation for the
celestial axes, and linear for any other axes.
- The TabOKTabOK attribute is set to a non-zero positive value in the FitsChan,
and the longitude and latitude axes are separable. In this case the Mapping will
be described by a pair of 1-dimensional look-up tables, using the “-TAB”
algorithm described in FITS-WCS paper III.
If none of the above conditions hold, the write operation will be
unsuccessful.