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The torus-based semi-analytical appr...

Xu, Chen.

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The torus-based semi-analytical approach in spaceborne gravimetry.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	The torus-based semi-analytical approach in spaceborne gravimetry./
Author:	Xu, Chen.
Description:	183 p.
Notes:	Source: Dissertation Abstracts International, Volume: 69-04, Section: B, page: 2178.
Contained By:	Dissertation Abstracts International69-04B.
Subject:	Geodesy. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=NR38132
ISBN:	9780494381328

The torus-based semi-analytical approach in spaceborne gravimetry.
Xu, Chen.

The torus-based semi-analytical approach in spaceborne gravimetry. - 183 p.

Source: Dissertation Abstracts International, Volume: 69-04, Section: B, page: 2178.

Thesis (Ph.D.)--University of Calgary (Canada), 2008.

Finally, a summarized and comprehensive calculating procedure for the general applications of gravity field determination from satellite missions is proposed.

ISBN: 9780494381328Subjects--Topical Terms:

550741
Geodesy.

The torus-based semi-analytical approach in spaceborne gravimetry.
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020 $a 9780494381328
035 $a (UMI)AAINR38132
035 $a AAINR38132
040 $a UMI $c UMI
100 1 $a Xu, Chen. $3 1031072
245 1 4 $a The torus-based semi-analytical approach in spaceborne gravimetry.
300 $a 183 p.
500 $a Source: Dissertation Abstracts International, Volume: 69-04, Section: B, page: 2178.
502 $a Thesis (Ph.D.)--University of Calgary (Canada), 2008.
520 $a Finally, a summarized and comprehensive calculating procedure for the general applications of gravity field determination from satellite missions is proposed.
520 $a The main objective of this research is to present a complete and comprehensive analysis of the torus-based semi-analytical approach of gravity field determination from spaceborne gravimetry observations. The focus is placed on the torus-based approach because it theoretically saves computational time and memory storage as a result of using both a two-dimensional fast Fourier transform (2D FFT) technique and the block-diagonal structured normal matrix in least-squares adjustment. However, the full implementation of this approach for practical applications has never been done.
520 $a Starting with an introduction of the theoretical and mathematical backgrounds of several state-of-art gravity field determination approaches, namely the direct, space-wise, time-wise, and torus-based semi-analytical approaches, the strengths and weaknesses of each approach are discussed. A complete and detailed calculating flow chart of the torus-based approach is developed. Under the assumption of a nominal orbit, the approach basically recovers the Earth's global gravity field in three major steps. In the first step, the in situ contaminated satellite observations, such as the disturbing potential data from the CHAMP mission or the gravity gradient tensor components from the GOCE mission, are reduced and interpolated onto a nominal torus grid. The second step is to calculate the pseudo-observables, the lumped coefficients Amk, using a 2D FFT technique. In the final step, spherical harmonic coefficients are estimated separately for the individual orders by least-squares adjustment. Several critical issues involved in the calculations have to be investigated. These issues are: filtering observations contaminated by colored noise, reducing height and inclination variations onto a nominal orbit, interpolating a torus grid, analyzing the aliasing problems in both spatial and spectral domains, calculating a weight matrix from an error power spectral density (PSD) model, investigating the regularization techniques in a nearly ill-posed problem of the normal matrix, determining the optimal weighting factors for the combined solution, and iterating the estimated solution.
520 $a Several case studies on the processing of satellite observations using the complete calculating flow are described and analyzed. The comparisons between the direct and torus-based approach show that the latter achieves the same accuracy level as the former with only 1% of the calculating time. Two groups of solutions, namely the stand-alone and the combined solutions, are obtained. The disturbing potential data from CHAMP and GRACE are able to recover the gravity field up to L = 70. However, the gravity field determined from the GRACE-type line-of-sight (Los) gradiometry data is not successful because the ≈ 220 km inter-satellite baseline of GRACE breaks the assumption that the baseline should be sufficiently small. In addition, the solutions of the gravity gradient tensor data from GOCE do not provide enough accuracy because the interpolation errors reach 3% of the original values. It is very easy to combine different types of observations or data sets using the torus-based approach. The combined (overall) solutions using the optimal weights determined by the variance components approach are better than the individual stand-alone solutions or equal-weighted overall solutions.
590 $a School code: 0026.
650 4 $a Geodesy. $3 550741
690 $a 0370
710 2 $a University of Calgary (Canada). $3 1017619
773 0 $t Dissertation Abstracts International $g 69-04B.
790 $a 0026
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=NR38132