On the indirect effect in the Stokes-Helmert method of geoid determination

The classical integral formula for determining the indirect effect in conne ction with the Stokes-Helmert method is related to a planar approximation o f the sea level. A strict integral formula, as well as some approximations to it, are derived. It is concluded that the capsize truncated integral for mulas will suffer from the omission of some long-wavelength contributions, of the order of 50 cm in high mountains for the classical formula. This lon g-wavelength information can be represented by a set of spherical harmonic coefficients of the topography to, say, degree and order 360. Hence, for pr actical use, a combination of the classical formula and a set of spherical harmonics is recommended.