|struct wcserr *||err|
Returned celprm struct members must not be modified by the user.
(Given and returned) This flag must be set to zero whenever any of the following celprm struct members are set or changed:
(Given) If true (non-zero), an offset will be applied to to force = (0,0) at the fiducial point, (,). Default is 0 (false).
(Given) The native longitude, [deg], and ...
(Given) The first pair of values should be set to the celestial longitude and latitude of the fiducial point [deg] - typically right ascension and declination. These are given by the
CRVALia keywords in FITS.
(Given and returned) The second pair of values are the native longitude, [deg], and latitude, [deg], of the celestial pole (the latter is the same as the celestial latitude of the native pole, ) and these are given by the FITS keywords
LATPOLEa (or by
PVi_3a attached to the longitude axis which take precedence if defined).
LONPOLEa defaults to (see above) if the celestial latitude of the fiducial point of the projection is greater than or equal to the native latitude, otherwise + 180 [deg]. (This is the condition for the celestial latitude to increase in the same direction as the native latitude at the fiducial point.) ref may be set to
UNDEFINED (from wcsmath.h) or 999.0 to indicate that the correct default should be substituted.
, the native latitude of the celestial pole (or equally the celestial latitude of the native pole, ) is often determined uniquely by
LONPOLEa in which case
LATPOLEa is ignored. However, in some circumstances there are two valid solutions for and
LATPOLEa is used to choose between them.
LATPOLEa is set in ref and the solution closest to this value is used to reset ref. It is therefore legitimate, for example, to set ref to +90.0 to choose the more northerly solution - the default if the
LATPOLEa keyword is omitted from the FITS header. For the special case where the fiducial point of the projection is at native latitude zero, its celestial latitude is zero, and
LONPOLEa = 90.0 then the celestial latitude of the native pole is not determined by the first three reference values and
LATPOLEa specifies it completely.
The returned value, celprm::latpreq, specifies how
LATPOLEa was actually used.
(Given and returned) Projection parameters described in the prologue to prj.h.
(Returned) Euler angles and associated intermediaries derived from the coordinate reference values. The first three values are the -, -, and -Euler angles [deg], and the remaining two are the cosine and sine of the -Euler angle.
(Returned) For informational purposes, this indicates how the
LATPOLEa keyword was used
(Returned) True if the spherical rotation preserves the magnitude of the latitude, which occurs iff the axes of the native and celestial coordinates are coincident. It signals an opportunity to cache intermediate calculations common to all elements in a vector computation.
(Returned) If enabled, when an error status is returned this struct contains detailed information about the error, see wcserr_enable().
|void * celprm::padding|
(An unused variable inserted for alignment purposes only.)
Global variable: const char *cel_errmsg - Status return messages Status messages to match the status value returned from each function.