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astGetMapping
-
Obtain a Mapping that converts between two Frames in a FrameSet
- Description:
- This function returns a pointer to a Mapping that will convert
coordinates between the coordinate systems represented by two
Frames in a FrameSet.
- Synopsis:
- AstMapping
astGetMapping( AstFrameSet
this, int iframe1, int iframe2 )
- Parameters:
-
this
-
Pointer to the FrameSet.
-
iframe1
-
The index of the first Frame in the FrameSet. This Frame describes
the coordinate system for the "input" end of the Mapping.
-
iframe2
-
The index of the second Frame in the FrameSet. This Frame
describes the coordinate system for the "output" end of the
Mapping.
- Returned Value:
-
astGetMapping()
-
Pointer to a Mapping whose forward transformation converts
coordinates from the first coordinate system to the second
one, and whose inverse transformation converts coordinates in
the opposite direction.
- Notes:
- The returned Mapping will include the clipping effect of any
Regions which occur on the path between the two supplied Frames
(this includes the two supplied Frames themselves).
- The values given for the "iframe1" and "iframe2" parameters
should lie in the range from 1 to the number of Frames in the
FrameSet (as given by its Nframe attribute). A value of
AST__BASE or AST__CURRENT may also be given to identify the
FrameSet's base Frame or current Frame respectively. It is
permissible for both these parameters to have the same value, in
which case a unit Mapping (UnitMap) is returned.
- It should always be possible to generate the Mapping
requested, but this does necessarily guarantee that it will be
able to perform the required coordinate conversion. If
necessary, the TranForward and TranInverse attributes of the
returned Mapping should be inspected to determine if the
required transformation is available.
- A null Object pointer (AST__NULL) will be returned if this
function is invoked with the AST error status set, or if it
should fail for any reason.
Next: astGetRefPos - Return the reference position in a specified celestial coordinate system
Up: AST Function Descriptions
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AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2009 Science \& Technology Facilities Council