Dictionary:Geodetic Reference System 1967 (GRS67)

The gravity field (acceleration of gravity) at the latitude ${\displaystyle \lambda }$ is given by
${\displaystyle g=978031.846\left(1+0.005278895\sin ^{2}(\lambda )+0.000023462\sin ^{4}(\lambda )\right){\text{mGal}}.}$
${\displaystyle 1.3049\sin 2\lambda \ \ {\frac {mGal}{mile}}=0.8108\sin 2\lambda \ \ {\frac {MGal}{km}}.}$