Mappings Available
The basic concept of a MappingMapping (§2.1) is rather
generic and obviously it is necessary to have specific Mappings that
implement specific relationships between coordinate systems. AST
provides a range of these, to perform transformations such as the
following and, where appropriate, their inverses:
- Conversions between various celestial coordinate systems (the
SlaMapSlaMap).
- Conversions between various spectral coordinate systems (the
SpecMapSpecMap and GrismMapGrismMap).
- Conversions between various time systems (the TimeMapTimeMap).
- Conversion between 2-dimensional spherical celestial coordinates
(longitude and latitude) and a 3-dimensional vectorial positions (the SphMapSphMap).
- Various projections of the celestial sphere on to 2-dimensional
coordinate spaces—i.e. map projections (the DssMapDssMap and WcsMapWcsMap).
- Permutation, introduction and elimination of coordinates (the
PermMapPermMap).
- Various linear coordinate transformations (the MatrixMapMatrixMap, WinMapWinMap,
ShiftMapShiftMap and ZoomMapZoomMap).
- General N-dimensional polynomial transformations (the PolyMapPolyMap and
ChebyMapChebyMap).
- Lookup tables (the LutMapLutMap).
- General-purpose transformations expressed using arithmetic
operations and functions similar to those available in C (the
MathMapMathMap).
- Transformations for internal use within a program, based on
private transformation functions which you write yourself in C (the
IntraMapIntraMap).
Further reading: For a more complete description of each of the
Mappings mentioned above, see its entry in
Appendix D. In addition, see the discussion of the
PermMap in §5.11, the UnitMapUnitMap in
§5.10 and the IntraMap in
§20. The ZoomMap is used as an example throughout
§4.