How WGS 84 defines the Earth

Besides being a map/chart datum, WGS 84 (World Geodetic System of 1984) also defines the shape and size of the ellipsoid of revolution that was considered the best representation of the Earth at that time:

Flattening = f =

1/298.257223563  (= ca. 3.35 ‰)

Semi-major axis = equatorial radius = a =

6 378 137.0 m

From these two numbers it is possible to calculate:

Semi-minor axis = polar radius = b = (1–f)a =

6 356 752.3142 m

Difference between equatorial and polar radius = a–b =

     21 384.6858 m


First eccentricity squared = e2 = 2f–f2 = 1–(b/a)2 =

0.00669437999014

First eccentricity = e =

0.081819190842622


Surface area of the Earth = 2pa2 + p(b2/e)ln[(1+e)/(1–e)] =


          510 065 621.724 km2

Volume of the Earth = (4/3)pa2b =

1 083 207 319 801 km3


Maximum circumference of the Earth =
circumference of the Earth at the equator =
circumference of parallel of latitude at 0° latitude = 2pa =

40 075.017 km

Minimum circumference of the Earth =
circumference of the Earth through the poles =
4 × (distance from a pole to the equator) =

40 007.863 km (see the main table)

Difference between maximum and minimum circumference =

       67.154 km

Calculated by Sigurd Humerfelt (25th January 2000, updated 17th April and 14th September 2000).