Tests and combination of satellite determinations of the gravity field with gravimetry

Six solutions for the tesseral harmonic coefficients of the geopotential from analyses of satellite orbits were compared with terrestrial gravimetry in the form of mean free-air anomalies of squares 300 nautical miles (n.m) on a side. Statistical parameters calculated were the mean-square values of each type of determination as well as the mean-square difference for different samples based on the number of observations in the 300-n.m. square. The study showed significant variation in quality between different solutions, the best being that recently obtained from camera tracking of satellites by Gaposhkin. The arithmetic mean of four independent satellite solutions was better than any single solution. This combined satellite solution was used in an adjustment with the gravimetry to obtain a single best solution, given herein in the forms of a geoid map; spherical harmonic coefficients to degree and order 12, 12; and gravity anomalies at 10° intervals.