Determination of local empirical covariance functions from residual terrain reduced altimeter data
Loading...
Date
1988-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University. Division of Geodetic Science
Abstract
Local empirical covariance functions have been estimated from cross-over adjusted high-pass filtered SEASAT/GEOS-3 altimeter data in three local 2° x 2° areas in the North Atlantic ocean. The high-pass filtering was needed in order to remove remaining long wavelength parts of the gravity field due to errors in the spherical harmonic expansion that was used, and effects from sea surface topography and correlated parts of radial orbit errors. After a subtraction of noise variances geoid height variances associated with harmonic degrees above 180 of 0.213 m2 , 0.112 m2 , and 1.217 m2 were obtained in the three local areas respectively. Then residual terrain effects were computed from Airy-Heiskanen isostatic earth models using Fourier techniques and "SYNBAPS" bathymetry. The depths of compensation were increased in order to simulate regional Vening Meinesz models. Comparisons of altimetric and bathymetric geoid heights showed that the magnitudes of the unmodelled parts of the gravity fields practically were unaffected by changes in the depths of compensation from 50 km to 70 km. Estimations of local empirical covariance functions from the terrain reduced altimetry showed that the geoid height variances were reduced by about 3 dB, 0 dB, and 9 dB to values of 0.096 m2 , 0.108 m2 , and 0.147 m2 respectively. The variances have hereby decreased to about the same level. [Full text of abstract available in document.]