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

RETURNED:

sla_DSEP

D

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.