formula.expert

Constants library

3 values, each with its units, its uncertainty, and where it came from.

Astronomical 3

Earth Equatorial Radius exact

a⊕=6,378,137 ma_\oplus = 6,378,137\ \text{m}

mSemi-major axis of the WGS 84 reference ellipsoid, exactly 6 378 137 m — the equatorial radius every GPS receiver is built around.

Earth Polar Radius exact

b⊕=6356752.314245 mb_\oplus = 6356752.314245\ \text{m}

mSemi-minor axis of the WGS 84 ellipsoid, 6 356 752.3 m — 21.4 km shorter than the equatorial radius because the Earth is spinning.

Earth Mean Radius

R⊕=6371008.8 mR_\oplus = 6371008.8\ \text{m}

mMean radius (2a + b)/3 of the WGS 84 ellipsoid, about 6371 km — the single figure used when a spherical Earth is good enough.