High degree spherical harmonic expansion of gravity data |
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| Authors: | Dezsö Nagy |
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| Institution: | (1) Gravity and Geodynamics Division Earth Physics Branch, Department of Energy, Mines and Resources, Ottawa, Ontario, Canada |
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| Abstract: | A spherical harmonic expansion of the gravity field up to degree and order 200 was carried out. Free air anomaly data over
Canada (10×10 block averages) with a range of 211.1 mgal were used for testing. A low degree expansion (N=30) produced a map with a range
of 63.6 mgal with contour patterns that could hardly be correlated with the original hand contoured map. A high degree expansion
(N=200) on the other hand resulted in a map with a range of 199.8 mgal which quite faithfully reproduced the original including
its local variations. Test computations verify that by monitoring the RMS values and the range of the expansion it is possible
to arrive at an optimum degree of expansion for a given data set. It was also verified by the computations, that, since the
computed expansions essentially have a zero value outside the domain of the input, it is possible to combine the results of
separate non-overlapping expansions.
Contribution of the Earth Physics Branch No. 900. Presented at the 1977 Spring Meeting, AGU, May 30–June 3, Washington, D.C. |
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