Spheroid

A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes.

Related Topics:
Quadric - Surface - Ellipse

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If the ellipse is rotated about its major axis, the surface is called a prolate spheroid (similar to the shape of a rugby ball or cigar).

Related Topics:
Rugby - Cigar

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If the minor axis is chosen, the surface is called an oblate spheroid (similar to the shape of the planet Earth).

Related Topics:
Oblate spheroid - Planet Earth

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A spheroid can also be characterised as an ellipsoid having two equal semi-axes, as represented by the equation

Related Topics:
Ellipsoid - Semi-axes

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:rac{x^2}{a^2}+rac{y^2}{b^2}+rac{z^2}{b^2}=1

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A prolate spheroid has one semiaxis longer than the other two, (a > b); an oblate spheroid has one semiaxis shorter than the other two (a < b) and can resemble a disk.

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Prolate spheroid.

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Oblate spheroid. -->

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The sphere is a special case of the spheroid in which the generating ellipse is a circle.

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