» Ellipticity redirects here. For the mathematical topic of ellipticity, see elliptic operator. The flattening, ellipticity, or oblateness of an oblate spheroid's the "squashing" of the spheroid's pole, towards its equator. First and second flattening The first, primary flattening, f,'s the versine of the spheroid's angular eccentricity ("o!varepsilon,!"), equalling the relative difference between its equatorial radius, a,!, and its polar radius, b,!: » ::f=mbox;,! Flattening without picking Fl… (More on Flattening)