- differentiate a sphere from an ellipsoid
calculate the flattening ratio, equator to polar circumference, of an ellipsoid
- f = (a - b) / a
- flattening, a = equitorial radius, b = polar radius
Earth is not a perfect sphere. It is oblong, with the equator being longer than the prime meridian. This is due, in part, to the rotation of the Earth.
An ellipsoid is a representation of the Earth's surface. There have been several ellipsoids developed over the past centuries, some with greater accuracy than others.