Effect of certain anomaly correction terms on potential coefficient determinations of the earth’s gravitational field

Abstract

For proper computation of the Stokes’ constants, or the evaluation of potential coefficients from terrestrial gravity data, surface free-air anomalies should be corrected to sea level. Such a correction is composed of two parts; the first, the Molodensky correction, G₁, and a second, a term depending on the degree (n) and the expansion of (hΔg). This paper examines these terms numerically, computing for 1654 5° equal area blocks values of G₁ and the total correction based on spherical harmonic expansions to degree 20. The largest correction found was 0.37 mgals. Corrections to potential coefficients caused by the anomaly correction were computed and compared to the original coefficients. The ratio between the coefficient corrections and the full coefficients generally increased by degree having a maximum ratio of 0.21 percent at degree 14 indicating that at the present time the corrections considered are negligible up to at least degree 20.