Earth's gravity field to the sixteenth degree and station coordinates from satellite and terrestrial data

Geodetic parameters describing the earth's gravity field and the positions of satellite-tracking stations in a geocentric reference frame have been computed. These parameters were estimated by means of a combination of four different types of data: routine and simultaneous satellite observations, observations of deep-space probes, and measurements of terrestrial gravity. This combination solution gives better parameters than any subset of data types. In the dynamic solution, precision-reduced Baker-Nunn observations and laser range data of 21 satellites were used. Data from optical cameras, in addition to those from 19 Baker-Nunn stations, were used in the geometrical solution. Data from the tracking of deep-space probes were used in the form of relative station longitudes and distances to the earth's axis of rotation. The surface-gravity data in the form of mean anomalies for 300-n.mi. squares were provided by Kaula. The adopted solution from each iteration was a combination solution and was chosen to improve the residuals of all types of data. In addition to these four data sets, astrogeodetic data, surface triangulation, and some recently acquired surface-gravity data not included in the set used for the combinations were used for an independent test of the solution. The total gravity field is represented by spherical harmonic coefficients complete to degree and order 16, plus a number of higher-degree terms. The half-wavelength resolution of this global solution subtends about 11° at the earth's center. The accuracy of the global field has been estimated as ±3 meters in geoid height, or ±8.7 mgal. Coordinates of many of the stations are determined with an accuracy of 10 meters or better.