Improving Resolution of Airborne Gravimetric System by Using of Wavelets Shrinkage De-noising

X.P. Li and C. Jekeli

Abstract:	Gravity surveying using airborne INS and GPS is receiving more and more attention from the geodetic community due to its great potential for determining the local geoid. For such an airborne gravimetric system, obtaining precise accelerations of GPS and INS is one of the fundamental issues. This paper describes the improvements in accuracy and resolution obtained by using wavelet shrinkage de-noising. To remove noise from observations, one could use standard smoothing techniques, such as B-spline smoothing, that remove the high frequency content of a signal, which is assumed to be noise. However, high frequency content does not necessarily belong to noise only, and noise could be present over a broad range of frequencies. Wavelet shrinkage de-noising is an effective approach to separate the noise from the signal. It attempts to remove whatever noise is present and retain whatever signal is present without requiring any assumptions about the nature of the signal, because the wavelet transform can characterize noise at different frequencies. The process consists of three fundamental steps: linear forward wavelet transform; de-noising by shrinkage, i.e., nonlinear soft thresholding; and linear inverse wavelet transform. Various kinds of wavelet de-noising routines can be established by combining different wavelet bases and thresholding schemes. Among them, the Hybrid Stein’s Unbiased Estimate of Risk (Sure) Shrink scheme is simple to implement and has broad adaptivity properties. To deal with irregularly spaced time domain data (e.g., due to GPS cycle slips and loss of lock), the second generation wavelets developed by Sweldens and Schröder can be used.
Published in:	Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004) June 7 - 9, 2004 Dayton Marriott Hotel Dayton, OH
Pages:	491 - 496
Cite this article:	Li, X.P., Jekeli, C., "Improving Resolution of Airborne Gravimetric System by Using of Wavelets Shrinkage De-noising," Proceedings of the 60th Annual Meeting of The Institute of Navigation (2004), Dayton, OH, June 2004, pp. 491-496.
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