Spherical coordinates to Cartesian coordinates (single precision).
CALL:
CALL sla_CS2C (A, B, V)
GIVEN:
A,B
R
spherical coordinates in radians:
etc.
RETURNED:
V
R(3)
unit vector
NOTE:
The spherical coordinates are longitude (+ve anticlockwise
looking from the +ve latitude pole) and latitude. The
Cartesian coordinates are right handed, with the x-axis
at zero longitude and latitude, and the z-axis at the
+ve latitude pole.