User Contributed Dictionary
 present participle of flatten
Extensive Definition
 Ellipticity redirects here. For the mathematical topic of ellipticity, see elliptic operator.
The flattening, ellipticity, or oblateness of an
oblate
spheroid is the "squashing" of the spheroid's pole,
down towards its equator.
First and second flattening
The first, primary flattening, f, is 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=\operatorname(o\!\varepsilon)=2\sin\left(\frac\right)^2=1\cos(o\!\varepsilon)=\frac;\,\!


 The flattening of the Earth in WGS84 is 1:298.257223563 (which corresponds to a radius difference of 21.385 km of the Earth radius 6378.137  6356.752 km) and would not be realized visually from space, since the difference represents only 0.335 %.
 The flattening of Jupiter (1:16) and Saturn (nearly 1:10), in contrast, can be seen even in a small telescope;
 Conversely, that of the Sun is less than 1:1000 and that of the Moon barely 1:900.
The amount of flattening depends on

 the relation between gravity and centrifugal force;

 size and density of the celestial body (see Figure of the Earth, last chapter);
 the rotation of the planet or star;
 and the elasticity of the body.
There is also a second flattening, f' (sometimes
denoted as "n"), that is the squared halfangle tangent of
o\!\varepsilon\,\!:


 f'=\tan\left(\frac\right)^2=\frac=\frac;\,\!

Flattening without picking
Flattening without picking is an efficient fullvolume automatic densepicking method for flattening seismic data. First, local dips (stepouts) are calculated over the entire seismic volume. The dips are then resolved into time shifts (or depth shifts) relative to reference trace using a nonlinear GaussNewton iterative approach that exploits Discrete Cosine Transforms (DCT's) to minimize computation time. At each point in the image two dips are estimated; one dip in the x direction and one dip in the y direction. Because each point in the image has two dips, each horizon is estimated from an overdetermined system of dips in a leastsquares sense.See also
flattening in Danish: Fladtrykthed
flattening in German: Abplattung
flattening in French: Aplatissement
flattening in Dutch: Afplatting
flattening in Japanese: 扁平率
flattening in Slovak: Sploštenie
flattening in Serbian: Елиптицитет
flattening in Swedish: Avplattning
flattening in Chinese: 扁率