An estimate of equatorial gravity from terrestrial and satellite data

• Published in: Geophysical research letters Vol. 14; no. 7; pp. 730 - 732
• Main Author: Rapp, Richard H.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.07.1987
• Subjects: Anomalies; Doppler effect; Estimates; Geophysics; Gravitation; Gravity anomalies; Satellites; Spherical harmonics
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/GL014i007p00730

Equatorial gravity has been estimated from terrestrial gravity data and from satellite implied data. The terrestrial estimate was based on the analysis of 43271 1°×1° mean free air gravity anomalies. The value estimated was 978032.35±0.5 mgals. This value may be slightly (0 to 1.5 mgals) too low because of the neglect of the downward continuation of surface free air anomalies to the geoid. An alternate estimate based on the comparison of terrestrial anomalies and altimeter derived anomalies yields 978032.6 mgals. Equatorial gravity from space data depends on GM from Lageos and lunar laser data and on a new estimate (6378136.2±0.5 m) of the equatorial radius based on Doppler tracking station positions and a new spherical harmonic expansion of the earth's gravity field to degree 360. The resultant equatorial gravity is 978032.78±0.2 mgals. The difference between the two terrestrial estimates is 0.4 and 0.2 mgals (or 0.4 ppm or 0.2 ppm). The agreement is within the accuracy of the two separate estimates. These comparisons can put constraints on parameters of non‐Newtonian force models.