Intersection of two arcs on sphere I have two arcs on a sphere that are defined as pair of points: $(\theta_0, \varphi_0)$, $(\theta_1, \varphi_1)$. I need to find a point where they intersect, or some indication if they don't. What is important is that they are arcs, not circles, so it is important to find intersection that is on the arcs specifically (not on projected circles). Arcs are meant to be shortest possible arcs. I am failing to find any specific equations on the internet. Thanks!

You can find a javascript implementation here: 
http://www.movable-type.co.uk/scripts/latlong.html
and a good explanation here:
http://www.boeing-727.com/Data/fly%20odds/distance.html
