# Prolate spheroid eccentricity (c>a)

## Description

A spheroid, or ellipsoid of revolution is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A prolate spheroid is a spheroid in which the polar axis is greater than the equatorial diameter ( like an American football or rugby ball). The prolate spheroid is generated by rotation about the Oz axis of an ellipse with semi-major axis c and semi-minor axis a, therefore e may again be identified as the eccentricity.

Related formulas## Variables

e | Eccentricity (dimensionless) |

a | Semi-major axis ( the equatorial radius of the spheroid) (dimensionless) |

c | Distance from centre to pole along the symmetry axis (c>a) (dimensionless) |