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SphMap

Map 3d Cartesian to 2d spherical coordinates
 Description:
 A SphMap is a Mapping which transforms points from a
3dimensional Cartesian coordinate system into a 2dimensional
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: Stc  Represents an instance of the IVOA STC class
Up: AST Class Descriptions
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AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. WarrenSmith & D.S. Berry
25th February 2013
Email:starlink@jiscmail.ac.uk
Copyright (C) 2014 Science \& Technology Facilities Council