# Modeling the Earth

Represent the shape and size of the Earth; represent ellipsoids; convert between parameters

## Functions

 `geocrs` Geographic coordinate reference system object `wgs84Ellipsoid` Reference ellipsoid for World Geodetic System of 1984 `egm96geoid` Geoid height from Earth Gravitational Model 1996 (EGM96) `earthRadius` Mean radius of planet Earth `rcurve` Ellipsoidal radii of curvature `rsphere` Radii of auxiliary spheres
 `geocentricLatitude` Convert geodetic to geocentric latitude `parametricLatitude` Convert geodetic to parametric latitude `geodeticLatitudeFromGeocentric` Convert geocentric to geodetic latitude `geodeticLatitudeFromParametric` Convert parametric to geodetic latitude
 `axes2ecc` Eccentricity of ellipse from axes lengths `majaxis` Semimajor axis of ellipse `minaxis` Semiminor axis of ellipse `ecc2flat` Flattening of ellipse from eccentricity `flat2ecc` Eccentricity of ellipse from flattening `ecc2n` Third flattening of ellipse from eccentricity `n2ecc` Eccentricity of ellipse from third flattening

## Classes

expand all

 `oblateSpheroid` Oblate ellipsoid of revolution `referenceEllipsoid` Reference ellipsoid `referenceSphere` Reference sphere
 `AuthalicLatitudeConverter` Convert between geodetic and authalic latitudes `ConformalLatitudeConverter` Convert between geodetic and conformal latitudes `IsometricLatitudeConverter` Convert between geodetic and isometric latitudes `RectifyingLatitudeConverter` Convert between geodetic and rectifying latitudes

## Topics

• The Shape of the Earth

The Earth can be modeled with increasing precision as a perfect sphere, an oblate spheroid, an ellipsoid, or a geoid.

• Reference Spheroids

A reference spheroid is a model of a roughly-spherical astronomical body with a simplified geometry, such as a sphere with uniform radius or a standard ellipsoid.

• Work with Reference Spheroids

Use reference spheroids to create map projections, to calculate curves and areas on the surface of a spheroid, and to transform 3-D geodetic coordinates.