Gets an AST Object using an environment parameter KPG1_GTOBJ
First, attempt to interpret the parameter value as an HDS path. The HDS object must have a type of WCS, must be scalar, and must contain a single one-dimensional array component with name DATA and type _CHAR. This is the scheme used for HDS structures created by KPG1_WWRT.
If the above attempt fails, attempt to interpret the parameter value as an NDF name. If the NDF is opened succesfully, its WCS FrameSet is returned. If a FrameSet is required, its current Frame is returned if a Frame is required. Its base-current Mapping is returned if a Mapping is required. A Box covering the pixel grid and re-mapped into the current WCS Frame is returned if a Regin is required.
If the above attempt fails, and the parameter value ends with " .FIT" , attempt to interpret the
parameter value as the name of a FITS file. Open the FITS file and attempt to obtained an AST
FrameSet from the primary HDU headers.
If the above attempt fails, attempt to interpret the parameter value as the name of a text file containing either an AST object dump, or a set of FITS headers.
" ISA.." function which returns .TRUE. if an Object is of a
suitable class. This is ignored if CLASS is blank. Otherwise, an error is reported if th supplied
Object is not of the required class. If the group contains the AST dump of a Channel (of any class), then the Object returned via IAST will
be the Channel itself. The exception to this is that if the " Begin " line at the start of the dump ends
with the string " (Read)" , then the returned IAST Object will be the Object read from the Channel,
rather than the Channel itself. For instance, if the group contains the AST dump of a FitsChan, and the
first line of the dump is " Begin FitsChan(Read)" , then the returned IAST object will be the Object
read from the FitsChan, rather than the FitsChan itself. This facility is only available for
top level objects (e.g. FitsChans contained within FitsChans cannot be read in this way).