- Created 2008-11-16 08:05:06
- by Anton
Online calculator: Ellipsoid
Scalene ellipsoid
Ellipsoid ia a sphere-like surface for which all cross-sections are ellipses.
Equation of standard ellipsoid body in xyz coordinate system is
where a - radius along x axis, b - radius along y axis, c - radius along z axis.
The volume of an ellipsoid is given by the following formula:
The surface area of a general ellipsoid cannot be expressed exactly by an elementary function. Knud Thomsen from Denmark proposed the following approximate formula:
Spheroids
If any two of the three axes of an ellipsoid are equal, the figure becomes a spheroid (ellipsoid of revolution). There are two kinds of spheroid: oblate spheroid (lens like) and prolate spheroid (сigar like).
Volume of spheroid is calculated by the following formula:
Unlike ellipsoids, exact surface area formulas exist for spheroids:

For oblate spheroid (a = b > c):
where angular eccentricity

For prolate spheroid (a = b < c):
where angular eccentricity
The Earth's shape is similar to an oblate spheroid with a ≈ 6,378.137 km and c ≈ 6,356.752 km. According to formula, Earth's surface is about 510050983.92 square kilometers.



