An equatorial diameter greater than the polar diameter makes the Earth this type of spheroid
The Earth has an equatorial bulge of 42.77 
km (26.58 mi): that is, its diameter ... Rotation causes a distortion from this 
spherical shape; a common measure... [DOC] [TLE] The polar diameter of the Earth is slightly less than the equatorial ... [PAR] The polar diameter of the Earth is slightly less than the equatorial diameter.