DETERMINATION OF THE EARTH'S GEOID BY SATELLITE OBSERVATIONS
NAVAL WEAPONS LAB DAHLGREN VA
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Determinations of the geoid made by different authors have differed by more than forty meters in some geographic locations. The authors differed in the observations employed in the number of gravity coefficients they determined, and in a number of details in the method of solution. Experiments conducted with Doppler observations on satellites have shown moderate variations rarely as much as 30 meters in the geoid determined if the number of satellite orbital inclinations employed is reduced by one. Reduction of the number of gravity parameters used to represent the geoid also resulted in moderate variations in the principal geoid features, except under special circumstances which are described. Reducing the number of weeks of observations did not produce deviations greater than 25 meters. However, reducing the number of observing stations in addition resulted in distortions of the computed geoid which reached 100 meters. It appears that the most recent geoid heights determined from satellite observations are correct to about 20 meters at any location and that observational data being obtained and techniques of computation being utilized should improve the accuracy to 10 meters or better.
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