Struct Ellipsoid 

pub struct Ellipsoid {
    pub a: f64,
    pub f: f64,
    pub b: f64,
    pub e2: f64,
}

A reference ellipsoid defined by its semi-major axis and flattening.

All four fields are stored for fast access, but only two are independent (a and f). The derived fields b and e2 are computed at construction time (in const context) to avoid repeated work in hot paths.

Field summary

Field	Formula	Description
a	(input)	Semi-major axis (equatorial radius), meters
f	1 / inv_f	Flattening
b	a * (1 - f)	Semi-minor axis (polar radius), meters
e2	2f - f^2	First eccentricity squared

Fields

a: f64

Semi-major axis (equatorial radius) in meters.

f: f64

Flattening: f = (a - b) / a.

b: f64

Semi-minor axis (polar radius) in meters: b = a * (1 - f).

e2: f64

First eccentricity squared: e2 = 2f - f^2.

Implementations

impl Ellipsoid

pub const WGS84: Self

WGS-84 ellipsoid (EPSG:4326, NIMA TR8350.2).

The World Geodetic System 1984 is the reference frame used by GPS and the default for all rustial coordinate operations.

• a = 6 378 137.0 m
• 1/f = 298.257 223 563

pub const GRS80: Self

GRS-80 ellipsoid (EPSG:7019, IUGG 1980).

The Geodetic Reference System 1980 is used by NAD83 (North America) and ETRS89 (Europe). It is nearly identical to WGS-84 (difference in 1/f is ~0.0001) but is a distinct definition.

• a = 6 378 137.0 m
• 1/f = 298.257 222 101

pub const fn from_a_inv_f(a: f64, inv_f: f64) -> Self

Construct an ellipsoid from semi-major axis a (meters) and inverse flattening inv_f (dimensionless).

Inverse flattening is the standard geodetic convention because f itself is a very small number (~0.003 for Earth) and 1/f (~298.257) is easier to read and compare across standards.

Derived quantities

f  = 1 / inv_f
b  = a * (1 - f)
e2 = 2f - f^2

pub fn second_eccentricity_squared(&self) -> f64

Second eccentricity squared: e'2 = (a^2 - b^2) / b^2.

Used in Vincenty geodesic formulae and some map projections.

pub fn radius_of_curvature_n(&self, lat_rad: f64) -> f64

Radius of curvature in the prime vertical (N) at geodetic latitude lat_rad (radians).

N = a / sqrt(1 - e2 * sin^2(lat))

This is the distance from the surface to the polar axis along the ellipsoid normal. Used in geographic-to-ECEF conversion and UTM projection.

pub fn is_sphere(&self) -> bool

Whether this ellipsoid is effectively a sphere (f == 0).

Can be used to select simplified (spherical) code paths where the ellipsoidal correction is negligible.

Trait Implementations

impl Clone for Ellipsoid

fn clone(&self) -> Ellipsoid

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Ellipsoid

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Ellipsoid

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Ellipsoid

fn eq(&self, other: &Ellipsoid) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Ellipsoid

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for Ellipsoid

impl StructuralPartialEq for Ellipsoid