Documentation / @interstellar-tools/equations / flatteningOblateSpheroid

Function: flatteningOblateSpheroid()

function flatteningOblateSpheroid(a: number, c: number): number;

Defined in: cartography/flattening-oblate-spheroid.ts:39

Compute flattening ($f$) of an oblate spheroid.

Flattening quantifies how much an ellipsoid of revolution is "squashed" at the poles, using equatorial radius ($a$) and polar radius ($c$):

$$f=\frac{a-c}{a}$$

Notes:

• ($f$) is dimensionless.
• For a physically valid oblate spheroid with ($a\ge c>0$), ($0\le f<1$).
• Commonly used in geodesy/cartography (e.g., defining reference ellipsoids and deriving related parameters like eccentricity).

Parameters

Parameter	Type	Description
a	number	Equatorial radius ($a$) (finite, > 0).
c	number	Polar radius ($c$) (finite, > 0).

Returns

number

Flattening ($f$) (dimensionless).

Throws

If a or c is not a finite number.

Throws

If a <= 0 or c <= 0.

Example

// Earth (WGS84-ish radii in meters):
const a = 6378137.0;
const c = 6356752.314245;
const f = flatteningOblateSpheroid(a, c);

See

• https://en.wikipedia.org/wiki/Flattening Flattening (definition and geodesy usage)
• https://en.wikipedia.org/wiki/Reference_ellipsoid Reference ellipsoid (a, b/c, and flattening used to define ellipsoids)
• https://epsg.org/guidance-notes.html EPSG Guidance Notes (geodesy reference; ellipsoid parameters and derived quantities)