great circle - Finding distance between two coordinates in ellipsoid?

I have two sets of latitude and longitude.

How do I find the distance between the two locations if I assume the earth is a perfect ellipsoid (with an eccentricity of 0.0167)?

Answer

I would recommend checking out:
Spherical: http://www.movable-type.co.uk/scripts/latlong.html
Great-Circle: http://www.movable-type.co.uk/scripts/gis-faq-5.1.html