WGS-84 modeling constants:

Semi-major axis
a = 6378137.0 m

Semi-minor axis
b = 6356732.3142 m = a/(1-f)

Flattening of ellipsoid
f = 1.0/298.2572235630

Eccentricity of ellipsoid
e = 0.081819191 = (2f-f^2)^0.5

2nd zonal harmonic coeff. of gravitational potential
C2,0 = - 484.16685 x 10^-6

Earth's gravitational const. (with mass of atmosphere)
GM = 0.3986004418 x 10^15 m3/s2

Earth's angular velocity at equator
omega = 7292115 x 10^-11 radians/sec



Centimeter accuracy correction to this model:
http://www.nima.mil/GandG/wgs-84/egm96.html