(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 sin<sub>2</sub>**q** – 0.0000059 sin<sub>2</sub>2**q**) mgal.
;#;
\\

The latitude correction amounts to 1.307 sin2**q** mgal/mile = 0.812 sin2**q** 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.)