 A more recent theoretical formula for gravity as a function of latitude is the International Gravity Formula 1980 (IGF80), also based on the WGS80 ellipsoid but now using the Somigliana equation:  are the equatorial and polar semi-axes, respectively; is the spheroid's eccentricity, squared ; is the defined gravity at the equator and poles, respectively; (formula constant); Further details Somigliana Formula For the normal gravity of the sea level ellipsoid, i.e. elevation h = 0, this formula by Somigliana (1929) applies (after Carlo Somigliana (1860–1955)Biografie Somiglianas (ital.)):
Somigliana equation A more recent theoretical formula for gravity as a function of latitude is the International Gravity Formula 1980 (IGF80), also based on the WGS80 ellipsoid but now using the Somigliana equation: (formula constant); is the defined gravity at the equator and poles, respectively; are the equatorial and polar semi-axes, respectively; is the spheroid's squared eccentricity; Further details For the normal gravity of the sea level ellipsoid, i.e. elevation h = 0, this formula by Somigliana (1929) applies (after Carlo Somigliana (1860–1955)Biografie Somiglianas (ital.)):
A
Somigliana equation
A
(formula constant); is the defined gravity at the equator and poles, respectively;
R
eccentricity, squared ; is the defined gravity at the equator and poles, respectively; (formula constant);
squared eccentricity;
D
Somigliana Formula