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A numerical study of the analytical downward continuation error in geoid computation by EGM08
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
2011 (English)In: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943, Vol. 1, no 1, 2-8 p.Article in journal (Refereed) Published
Abstract [en]

Today the geoid can be conveniently determined by a set of high-degree spherical harmonics, such as EGM08 with a resolution of about 5'. However, such a series will be biased when applied to the continental geoid inside the topographic masses. This error we call the analytical downward continuation (DWC) error, which is closely related with the so-called topographic potential bias. However, while the former error is the result of both analytical continuation of the potential inside the topographic masses and truncation of a series, the latter is only the effect of analytical continuation.

This study compares the two errors for EGM08, complete to degree 2160. The result shows that the topographic bias ranges from 0 at sea level to 5.15 m in the Himalayas region, while the DWC error ranges from -0.08 m in the Pacific to 5.30 m in the Himalayas. The zero-degree effects of the two are the same (5.3 cm), while the rms of the first degree errors are both 0.3 cm. For higher degrees the power of the topographic bias is slightly larger than that for the DWC error, and the corresponding global rms values reaches 25.6 and 25.3 cm, respectively, at nmax=2160. The largest difference (20.5 cm) was found in the Himalayas. In most cases the DWC error agrees fairly well with the topographic bias, but there is a significant difference in high mountains. The global rms difference of the two errors clearly indicates that the two series diverge, a problem most likely related with the DWC error.

Place, publisher, year, edition, pages
2011. Vol. 1, no 1, 2-8 p.
Keyword [en]
Analytical continuation, downward continuation, topographic bias, EGM08
National Category
Other Engineering and Technologies
URN: urn:nbn:se:kth:diva-166661DOI: 10.2478/v10156-010-0001-8OAI: diva2:811762

QC 20150513

Available from: 2015-05-13 Created: 2015-05-13 Last updated: 2015-05-13Bibliographically approved

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Sjöberg, Lars E.Bagherbandi, Mohammad
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