An SlaMap is a specialised form of MappingMapping which can be used to represent a sequence of conversions between standard celestial (longitude, latitude) coordinate systems.
When an SlaMap is first created, it simply performs a unit (null) Mapping on a pair of coordinates. Using the astSlaAddastSlaAdd function, a series of coordinate conversion steps may then be added, selected from those provided by the SLALIB Positional Astronomy Library (Starlink User Note SUN/67). This allows multi-step conversions between a variety of celestial coordinate systems to be assembled out of the building blocks provided by SLALIB.
For details of the individual coordinate conversions available, see the description of the astSlaAdd function.