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The Mapping Class

Before we start, it is worth taking a quick look at the Mapping class as a whole and some of the sub-classes it contains:

   Mapping
      CmpMap
      DssMap
      GrismMap
      IntraMap
      LutMap
      MathMap
      MatrixMap
      PermMap
      PolyMap
      SlaMap
      SpecMap
      TimeMap
      UnitMap
      WcsMap
      ZoomMap

      Frame
         <various types of Frame>

The Frame sub-class has been separated out here because it is covered in detail in [*]. We start by looking at the parent class, Mapping.

AST does not provide a function to create a basic Mapping (i.e. the astMapping constructor does not exist). This is because the Mapping class itself is ``virtual'' and basic Mappings are of no use in themselves. The Mapping class serves simply to contain the various specialised Mappings that exist. However, it provides more than just a convenient heading for them because it bestows all classes of Mapping with common properties (e.g. attributes) and behaviour. By examining the Mapping class, we are therefore examining the things that all other Mappings have in common.


next up previous 264
Next: The Mapping Model
Up: Inter-Relating Coordinate Systems (Mappings)
Previous: Inter-Relating Coordinate Systems (Mappings)

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
7th December 2012
E-mail:starlink@jiscmail.ac.uk

Copyright (C) 2012 Science \& Technology Facilities Council