On a sphere the central angle between two points is defined as the angle whose vertex is the centre of the sphere and that subtends the arc formed by the great circle between the points. This function computes the central angle for two points \((\phi_1, \lambda_1)\) and \((\phi_2,\lambda_2)\).
central.angle(phi1, lambda1, phi2, lambda2)Latitude of first point
Longitude of first point
Latitude of second point
Longitude of second point
Central angle