The Computation of Detailed Geoids Using the Fast Fourier Transform Method
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Date
1989-08
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Publisher
Ohio State University. Division of Geodetic Science
Abstract
The fast method of geoid computation using fast Fourier transform techniques is summarized. The various errors related to the method are analyzed. Numerical computation involves a test area in the State of Tennessee where a GPS survey network consisting of 60 stations has been established. The gravity data used for the test are the 4 km x 4 km gridded free-air anomalies on the Albers-equal area projection plane with different grid sizes. Different degrees of the reference field are used to combine with local gravity data. Best results are found by using a high degree (180 or 360) reference field combined with local gravity data with a border chosen according to Rapp's rule, by which the border is approximately θ° = 180°/nref., nref. being the degree of reference field used. The comparison between the FFT-computed undulation differences and the ones by OPS-leveling agrees to about 1.3 to 2.6 ppm level for station separations shorter than 55 km. [Some mathematical expressions are not fully represented in the metadata. Full text of abstract available in document.]