Dome who bottom cross section takes the form of an ellipse
An elliptical dome, or an oval dome, is a
dome whose bottom
cross-section takes the form of an
ellipse.[1] Technically, an ellipsoidal dome has a circular cross-section, so is not quite the same.
While the
cupola can take different
geometries, when the ceiling's cross-section takes the form of an ellipse, and due to the reflecting properties of an ellipse, any two persons standing at a
focus of the floor's ellipse can have one whisper, and the other hears; this is a
whispering gallery.
A blue circle, graphed with a red ellipse. An elliptical dome has an elliptical base, and an ellipsoidal dome has a circular base.
An ellipse, the "reflecting," "whispering gallery" property of the foci F and F' illustrated: The distance from F to F' may be great, but a whisperer at F can be heard, as F'.
Both -a and a are points of the
x-axis and -b and b are points on the
y-axis
Elliptical domes have many applications in
architecture; and are useful in covering
rectangular spaces. The
oblate, or horizontal elliptical dome is useful when there is a need to limit height of the space that would result from a
spherical dome. As the
mathematical description of an elliptical dome is more complex than that of spherical dome, design care is needed.[5]
In a
geodesic dome with a circular base, the triangular elements align so their edges form
great circles. Although not geodesic, a new, elliptical design was patented in 1989; it uses
hexagons and
pentagons to form a dome with a cross section that is elliptical. Due to its mathematical derivation, this design is called "
geotangent".[6]
World examples
Elliptical domes come up in the design of all of the following: