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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Hsiao, Yu-ShenHas files: Yes

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Now showing 1 - 5 of 5
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    Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)
    (2010-12-01)
    Kim, Kwang Bae
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    Hsiao, Yu-Shen
    ;
    Kim, Jeong Woo
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    Lee, Bang Yong
    ;
    Kwon, Yi Kyun
    The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell's (SAS) approach (1994), GGM was found to have an advantage with short wavelength (<= 12 km) components, while SAS better predicts longer wavelength (>= 25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm(3) between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the "A" value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.
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    New free-air and Bouguer gravity fields of Taiwan from multiple platforms and sensors
    (2014-01-25)
    Hwang, Cheinway
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    Hsu, Hung-Jui
    ;
    Chang, Emmy T. Y.
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    Featherstone, W. E.
    ;
    Tenzer, Robert
    We construct 1' x 1' grids of free-air and Bouguer gravity anomalies around Taiwan with well-defined error estimates for quality assessment. The grids are compiled from land, airborne and shipbome gravity measurements, augmented with altimeter gravity at sea. Three sets of relative land gravity measurements are network-adjusted and outlier-edited, yielding accuracies of 0.03-0.09 mGal. Three airborne gravity sets are collected at altitudes 5156 and 1620 m with accuracies of 2.57-2.79 mGal. Seven offshore shipborne gravity campaigns around Taiwan and its offshore islands yield shallow-water gravity values with 0.88-2.35 mGal accuracies. All data points are registered with GPS-derived geodetic coordinates at cm-dm accuracies, allowing for precise gravity reductions and computing gravity disturbances. The various datasets are combined by the band-limited least-squares collocation in a one-step procedure. In the eastern mountainous (or offshore) region, Bouguer anomalies and density contrasts without considering the oceanic (or land) topographic contribution are underestimated. The new grids show unprecedented tectonic features that can revise earlier results, and can be used in a broad range of applications. (C) 2013 Elsevier B.V. All rights reserved.
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    Airborne Gravity Surveys Over Taiwan Island and Strait, Kuroshio Current and South China Sea: Comparison of GPS and Gravity Accuracies at Different Flight Altitudes
    (2012)
    Hwang, Cheinway
    ;
    Shih, Hsuan-Chang
    ;
    Hsiao, Yu-Shen
    ;
    Huang, Chi-Hsun
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    土木工程學系
    We compare the accuracies of GPS and gravity observations obtained from three airborne gravity surveys over Taiwan Island at altitude 5000 m and over Kuroshio Current, Taiwan Strait, and Dongsha Atoll at altitude 1500 m. A kinematic network adjustment was used to determine the positions of the aircrafts. GPS positioning errors are at the decimeter-level, which are not entirely propagated to velocity and acceleration errors due to cancellation of long wavelength errors. Outliers are downweighted in the Gaussian filtering to improve the gravity accuracy, especially at altitude 1500 m. Compared with the upward-continued gravity, the gravity anomalies from the 1500-m surveys show a consistent accuracy of about 3 mgal; the accuracy from the 5000-m survey is degraded, especially over high mountains. The RMS crossover differences at 1500 m and 5000 m are all below 3 mgal, suggesting flight altitudes do not affect the crossover difference. Coherence analysis suggests that the spatial resolvable wavelengths of the airborne gravity range from 4 km (altitude 1500 m) to 6 km (altitude 5000 m).
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    Data reduction in scalar airborne gravimetry: Theory, software and case study in Taiwan
    (2006-12-01)
    Hwang, Cheinway
    ;
    Hsiao, Yu-Shen
    ;
    Shih, Hsuan-Chang
    ;
    土木工程學系
    ;
    Department of Civil Engineering
    The objective of this paper is to present theories of scalar airborne gravimetry and to publish the related software to interested readers for free access. Numerical procedures and techniques are developed to compute velocities and accelerations from GPS-determined positions. A method based on the correlation analysis of raw gravity reading and vertical acceleration of aircraft is used to correct for gravimeter times. A method and a computer program for crossover adjustment of gravity values along survey lines are developed. This method allows flexible selection of a fixed survey line to overcome the rank defect problem. A computer program is developed to compute gravity anomalies while applying corrections of gravimeter position and filtering. Upward and downward continuations of gravity anomalies are performed using Fast Fourier Transform. Using observed airborne gravity data along a survey line and simulated data in Taiwan, all the programs have been validated and produced reliable results. (c) 2006 Elsevier Ltd. All rights reserved.
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    Geodetic and geophysical results from a Taiwan airborne gravity survey: Data reduction and accuracy assessment
    (2007-04-17)
    Hwang, Cheinway
    ;
    Hsiao, Yu-Shen
    ;
    Shih, Hsuan-Chang
    ;
    Yang, Ming
    ;
    Chen, Kwo-Hwa
    [ 1] An airborne gravity survey was conducted over Taiwan using a LaCoste and Romberg (LCR) System II air-sea gravimeter with gravity and global positioning system (GPS) data sampled at 1 Hz. The aircraft trajectories were determined using a GPS network kinematic adjustment relative to eight GPS tracking stations. Long-wavelength errors in position are reduced when doing numerical differentiations for velocity and acceleration. A procedure for computing resolvable wavelength of error-free airborne gravimetry is derived. The accuracy requirements of position, velocity, and accelerations for a 1-mgal accuracy in gravity anomaly are derived. GPS will fulfill these requirements except for vertical acceleration. An iterative Gaussian filter is used to reduce errors in vertical acceleration. A compromising filter width for noise reduction and gravity detail is 150 s. The airborne gravity anomalies are compared with surface values, and large differences are found over high mountains where the gravity field is rough and surface data density is low. The root mean square (RMS) crossover differences before and after a bias-only adjustment are 4.92 and 2.88 mgal, the latter corresponding to a 2-mgal standard error in gravity anomaly. Repeatability analyses at two survey lines suggest that GPS is the dominating factor affecting the repeatability. Fourier transform and least-squares collocation are used for downward continuation, and the latter produces a better result. Two geoid models are computed, one using airborne and surface gravity data and the other using surface data only, and the former yields a better agreement with the GPS-derived geoidal heights. Bouguer anomalies derived from airborne gravity by a rigorous numerical integration reveal important tectonic features.