SLA_DSEP - Angle Between 2 Points on Sphere   

ACTION:

Angle between two points on a sphere (double precision).

CALL:

D = sla_DSEP (A1, B1, A2, B2)

GIVEN:

A1,B1 spherical coordinates of one point (radians)

A2,B2 D spherical coordinates of the other point (radians)

RETURNED:

sla_DSEP angle between [A1,B1] and [A2,B2] in radians

NOTES:

1.

The spherical coordinates are right ascension and declination, longitude and latitude, etc., in radians.

2.

The result is always positive.