CTYPEia&All coordinate systems and projection types
listed in paper II are supported (note, “CUBEFACE” axes are treated as
unknown linear axes). In addition, "-HPX" (HEALPix) and "-XPH" (polar
HEALPix) are supported.&Determined by the SystemSystem attribute
of the SkyFrame and the WcsTypeWcsType attribute of the
WcsMapWcsMap within the FrameSet.
CUNITia&Ignored (assumed to be 'degrees').&Not written.
PVi_ma&Used to create the pixel to WCS MappingMapping (values
are stored as attributes of a WcsMap within this Mapping).&Values are
obtained from the WcsMap in the pixel to WCS Mapping.
LONPOLEa&Used to create the pixel to WCS Mapping. Also
stored as a PVi_mPVi_m attribute for the longitude axis of the WcsMap.&Only
written if not equal to the default value defined in paper II (see
“Choice of LONPOLE/LATPOLE” below).
LATPOLEa&Used to create the pixel to WCS Mapping. Also
stored as a PV attribute for the longitude axis of the WcsMap.&Only
written if not equal to the default value defined in paper II (see
“Choice of LONPOLE/LATPOLE” below).
RADESYSa&Used to set the attributes of the SkyFrame. All
values supported except that ecliptic coordinates are currently always
assumed to be FK5.&Always written. Determined by the System attribute of
the SkyFrame.
EQUINOXa&Used to set the EquinoxEquinox attribute
of the SkyFrame.&Written if relevant. Determined by the Equinox attribute of
the SkyFrame.
EPOCH&Used to set the Equinox attribute of the SkyFrame.&Only
written if using FITS-AIPS and FITS-AIPS++ encodings. Determined by the Equinox attribute
of the SkyFrame.
MJD-OBS&Used to set the EpochEpoch attribute of the
SkyFrame. DATE-OBS is used if MJD-OBS is not present. A default value based on
RADESYS and EQUINOX is used if used if DATE-OBS is not present
either.&Determined by the Epoch attribute of the SkyFrame. Only written
if this attribute has been set to an explicit value (in which case
DATE-OBS is also written).
|