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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/77028

    Title: 台灣GPS時間序列的雜訊分析;Noise analysis of GPS time series in Taiwan
    Authors: 李宥葭;Lee, You-Chia
    Contributors: 地球科學學系
    Keywords: GPS;時間序列;白雜訊;色雜訊;GPS;time series;white noise;color noise
    Date: 2018-08-24
    Issue Date: 2018-08-31 13:10:41 (UTC+8)
    Publisher: 國立中央大學
    Abstract: 板塊運動和地殼形變相關研究的資料以全球衛星定位系統(Global Positioning System,簡稱GPS)為基礎。在大部分GPS時間序列的研究中,資料誤差只考慮雜訊振幅與觀測時間無關的白雜訊(white noise)。但是近幾年來發現,如果不考慮雜訊振幅與時間相關的色雜訊(coloured noise),例如:flicker noise和random walk noise將會造成資料誤差的低估,準確度也受到影響。因此在本篇研究分析時間序列中的雜訊成分,並重新計算測站的速度誤差。本文考慮的GPS連續測站有541個,其中選用測站觀測長度大於2.5年的資料進行研究,觀測時間最長22年。這些測站具有各種不同的儀器基座,包括深錨淺錨柱式、屋頂型、淺錨柱式、水泥柱式等,在台灣淺錨柱式及屋頂式測站數量較多的基座型式,本研究找到519個測站的基座型式,其中淺錨柱式基座最多有227個測站(42%),其次為屋頂式基座203個測站(38%)。使用最大概似估計法(MLE)及功率頻譜(power spectrum)兩種方法進行分析,以了解時間序列中雜訊組成。結果顯示多數測站在南北向量的雜訊振幅最小,垂直向量的雜訊振幅最大,且W+F模型中white noise和flicker noise的雜訊振幅會呈正相關。針對不同基座型式的結果比較最佳雜訊模型、頻譜指數與速度誤差的穩定性,其中深錨柱式測站有較小的速度誤差,雜訊振幅大小也比其他基座型式更小、更穩定。;Global positioning system (GPS) is usually used for researches of plate tectonics and crustal deformation. In most studies, GPS time series considered only time-independent noises (white noise), but time-dependent noises (color noise: flicker noise, random walk noise) which were found by nearly twenty years are also important to the precision of data. The rate uncertainties of stations will be underestimated if the GPS time series are assumed only time-independent noise. Therefore, studying the noise properties of GPS time series is necessary in order to realize the precision and reliability of velocity estimates. The lengths of GPS time series are from 541 stations around Taiwan with time spans longer than 2.5 years up to 22 years. The GPS stations include different monument types such as deep drilled braced, roof, metal tripod, concrete pier etc., and the most common type in Taiwan are the metal tripod and roof. I investigated the noise properties of continuous GPS time series by using the spectral index and amplitude of the power law noise. During the process I first remove the data outliers, and then estimate linear trend, size of offsets, and seasonal signals, and finally the amplitudes of the power-law and white noise are estimated simultaneously. The results show that the noise amplitudes of the north component are smaller than that of the other two components, and the largest amplitudes are in the vertical. I also find that the amplitudes of white noise and power-law noises are positively correlated in three components. Amplitude of white noise do not change with time, called time-independent noise. Amplitude of flicker noise and random walk noise change with time, considered be time-dependent noise, called color noise. Comparisons of noise amplitudes of different monument types in Taiwan reveal that the deep drilled braced monuments have smaller velocity uncertainties and amplitudes, are more stable than other monuments.
    Appears in Collections:[地球物理研究所] 博碩士論文

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