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SphMap - Map 3-d Cartesian to 2-d spherical coordinates

Description:
A SphMap is a Mapping which transforms points from a 3-dimensional Cartesian coordinate system into a 2-dimensional spherical coordinate system (longitude and latitude on a unit sphere centred at the origin). It works by regarding the input coordinates as position vectors and finding their intersection with the sphere surface. The inverse transformation always produces points which are a unit distance from the origin (i.e. unit vectors).
Constructor Function:
astSphMap
Inheritance
The SphMap class inherits from the Mapping class.
Attributes
In addition to those attributes common to all Mappings, every SphMap also has the following attributes:

  • UnitRadius: SphMap input vectors lie on a unit sphere?

  • PolarLong: The longitude value to assign to either pole
Functions
The SphMap class does not define any new functions beyond those which are applicable to all Mappings.


next up previous 264
Next: Stc - Represents an instance of the IVOA STC class
Up: AST Class Descriptions
Previous: SpecMap - Sequence of spectral coordinate conversions

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
25th February 2013
E-mail:starlink@jiscmail.ac.uk

Copyright (C) 2014 Science \& Technology Facilities Council