(1) A correction of gravity data because ol variation in centrifugal force resulting from the earth's rotation as the distance to the earth's axis varies with latitude q and for variation of the earth's radius because of polar flattening. The International Gravity Formula (1930) for such variation is

g = 978,049 (1 + 0.0052884 sin₂q – 0.0000059 sin₂2q) mgal. ;#;

The latitude correction amounts to 1.307 sin2q mgal/mile = 0.812 sin2q mgal/km.

(2) A gyrocompass correction for the rotation of the horizontal north vector is a function of latitude. (The horizontal north vector is tangent to the earth and hence the rotation is the result of the earth curvature.)