The northern European geoid: a case study on long-wavelength geoid errors |
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| Authors: | O C D Omang R Forsberg |
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| Institution: | (1) Department of Mapping Sciences, P.O. Box 5034 NLH, Agricultural University of Norway, 1432 As, Norway e-mail: ove@omang.com; Tel.: +47 6494 8846; Fax.: +47 6494 8856, NO;(2) Geodynamic Department, National Survey and Cadastre (KMS), Rentemestervej 8, 2400 Copenhagen NV, Denmark e-mail: rf@kms.dk; Tel.: +45 3587 5319; Fax.: 45 3587 5052, NO |
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| Abstract: | The long-wavelength geoid errors on large-scale geoid solutions, and the use of modified kernels to mitigate these effects,
are studied. The geoid around the Nordic area, from Greenland to the Ural mountains, is considered. The effect of including
additional gravity data around the Nordic/Baltic land area, originating from both marine, satellite and ground-based measurements,
is studied. It is found that additional data appear to increase the noise level in computations, indicating the presence of
systematic errors. Therefore, the Wong–Gore modification to the Stokes kernel is applied. This method of removing lower-order
terms in the Stokes kernel appears to improve the geoid. The best fit to the global positioning system (GPS) leveling points
is obtained with a degree of modification of approximately 30. In addition to the study of modification errors, the results
of different methods of combining satellite altimetry gravity and other gravimetry are presented. They all gave comparable
results, at the 6-cm level, when evaluated for the Nordic GPS networks. One dimensional (1-D) and 2-D fast Fourier transform
(FFT) methods are also compared. It is shown that even though methods differ by up to 6 cm, the fit to the GPS is essentially
the same. A surprising conclusion is that the addition of more data does not always produce a better geoid, illustrating the
danger of systematic errors in data.
Received: 4 July 2001 / Accepted: 21 February 2002 |
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| Keywords: | : Kernel modification – Data combination techniques – Satellite altimetry data – Geoid |
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