TRUEthen all co-ordinate frames in the WCS component are written out. Otherwise, only the current Frame is written out.
!) the list of the FITS extension is reported directly to you.
If the NDF does not have a FITS extension the application will exit.
"FITS-IRAF" –- This uses keywords CRVALi CRPIXi, CDi_j, and is the system commonly
used by IRAF. It is described in the document “World Coordinate Systems Representations
Within the FITS Format” by R.J. Hanisch and D.G. Wells, 1988, available by ftp from
"FITS-WCS" –- This is the FITS standard WCS encoding scheme described in the paper
“Representation of celestial coordinates in FITS”
It is very similar to
"FITS-IRAF" but supports a wider range of projections and
"FITS-WCS(CD)" –- This is the same as
"FITS-WCS" except that the scaling and rotation
of the data array is described by CD matrix instead of a PC matrix with associated
"FITS-PC" –- This uses keywords CRVALi, CDELTi, CRPIXi, PCiiijjj, etc, as in a
previous (now superseded) draft of the above FITS world co-ordinate system paper by
E.W. Greisen and M. Calabretta.
"FITS-AIPS" –- This uses conventions described in the document “Non-linear Coordinate
Systems in AIPS” by Eric W. Greisen (revised 9th September, 1994), available by ftp
/fits/documents/wcs/aips27.ps.Z. It is currently employed by the
AIPS data analysis facility, so its use will facilitate data exchange with AIPS.
This encoding uses CROTAi and CDELTi keywords to describe axis rotation and
"FITS-AIPS++" –- This is an extension to
"FITS-AIPS" that allows the use of a wider
range of celestial projections, and is used by the AIPS++ project.
"FITS-CLASS" –- This uses the conventions of the CLASS project. CLASS is a software
package for reducing single-dish radio and sub-mm spectroscopic data. It supports
"DSS" –- This is the system used by the Digital Sky Survey, and uses keywords AMDXn,
AMDYn, PLTRAH, etc.
"Native" –- This is the native system used by the AST library (see SUN/210), and
provides a loss-free method for transferring WCS information between AST-based
application. It allows more complicated WCS information to be stored and retrieved than
any of the other encodings.