Function calculate_intersection 

pub fn calculate_intersection(
    pole1: &Vector3d,
    pole2: &Vector3d,
    min_sq_value: f64,
) -> Option<Vector3d>

Calculate an intersection point between the poles of two Great Circles. See: http://www.movable-type.co.uk/scripts/latlong-vectors.html#intersection

• pole1, pole2 the poles.
• min_sq_value the minimum square of a vector length to normalize.

return an intersection point or None if the poles represent coincident Great Circles.