This attribute specifies which type of FITS-WCS projection will be performed by a WcsMap. The value is specified when a WcsMap is first created using astWcsMap and cannot subsequently be changed.

The values used are represented by macros with names of the form " AST__XXX" , where " XXX" is the (upper case) 3-character code used by the FITS-WCS " CTYPEi" keyword to identify the projection. For example, possible values are AST__TAN (for the tangent plane or gnomonic projection) and AST__AIT (for the Hammer-Aitoff projection). AST__TPN is an exception in that it is not part of the FITS-WCS standard (it represents a TAN projection with polynomial correction terms as defined in an early draft of the FITS-WCS paper).

WcsMap

• For a list of available projections, see the FITS-WCS paper.