Ellipsoid
Ellipsoid parameters, radii, and auxiliary latitudes.
These tools describe the reference ellipsoid itself: its axes, flattening, and mean radii, its radii of curvature at a latitude, and the auxiliary latitudes used inside map projection and geodesic formulas. Developers and geodesy students use them to check constants and intermediate values. Start with the ellipsoid parameters for WGS 84 or GRS 80. One pitfall: the two ellipsoids differ slightly in flattening, so pick the one your datum actually uses.
I want to look up an ellipsoid's parameters
- Ellipsoid parameters
The defining and derived parameters of a reference ellipsoid: semi-minor axis, flattening, eccentricities, third flattening, and the mean, authalic, and volumetric radii.
I want to find the radius of curvature or the length of a degree
- Radii of curvature and degree lengths
At a latitude: the meridional and prime-vertical radii of curvature, their Gaussian mean, the radius in any azimuth, the length of one degree of latitude and longitude, and the meridian arc from the equator or between two latitudes.
I want to convert between geodetic and other latitudes
- Auxiliary latitudes
Converts between geodetic latitude and the geocentric, parametric (reduced), rectifying, conformal, authalic, and isometric latitudes, in either direction.