Analysis of the Effects of Satellite Distribution and Solar Activity on Positioning Accuracy Using Real-World Data

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/96378

Title:	Analysis of the Effects of Satellite Distribution and Solar Activity on Positioning Accuracy Using Real-World Data
Authors:	曾敏倫;Tseng, Min-Lun
Contributors:	數學系
Keywords:	全球定位系統;單頻單點定位;偽距觀測量定位法;電離層模型修正法;高斯牛頓法;精度衰減因子;Global Positioning System;Single Frequency Single Point Positioning;Pseudorange Measurement;Klobuchar Model;Gauss-Newton Method;Dilution of Precision
Date:	2025-01-22
Issue Date:	2025-04-09 18:23:12 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究針對單頻單點之全球定位系統(Global Positioning System, GPS)的真實數據，深入探討衛星分佈與太陽活動度對定位解精度的影響。研究首先對接收到的衛星信號數據進行資料預處理，提取偽距誤差模型所需的參數，並準確存取各時間點的定位衛星。完成定位解算後，將所有定位解數據取平均值，並以該平均值作為基準，進一步將各時間點的定位解轉換至東、北、上 (East-North-Up, ENU) 座標系，以量化定位點相對平均值的東西向、南北向與上下向偏移量。為排除異常偏差，移除了偏離平均值兩倍標準差之外的定位點數據。隨後，將所有定位解數據以24小時為週期進行時間摺疊，觀察定位解偏差是否在特定時段出現顯著增加的現象。實驗結果顯示，定位解在部分時間點出現顯著偏差，並且偏差量隨時間呈現明顯變化趨勢。此外，計算每個時間點的精度稀釋因子 (Dilution of Precision, DOP)，並繪製衛星走時圖 (Skyplot)，以直觀呈現衛星分佈狀況。這些指標用於評估衛星分佈和太陽活動對定位精度的綜合影響。實驗結果表明，較差的 DOP 值表明衛星幾何形狀較差的時期。這些時期與顯著的定位誤差部分重疊，說明衛星分佈對定位解偏差具有解釋作用。另一方面，F10.7太陽指數和擾動風暴時間 (Disturbance Storm Time, Dst) 指數的分析表明，雖然一些顯著的定位誤差與異常的太陽活動水平相吻合。這表明太陽活動增強可能引起電離層擾動並降低定位精度，但單靠太陽活動無法完全解釋所有觀測到的偏差。最後，研究檢視了偽距誤差模型中誤差項對定位精度的影響。實驗結果表明，衛星時鐘偏差對定位精度影響最大。 ;This study analyzes single-frequency, single-point GPS observational data to investigate the effects of satellite distribution and solar activity on positioning accuracy. First, during the data preprocessing stage, the parameters required for pseudorange error models were extracted, and the satellites used for positioning at each time point were identified. Subsequently, positioning solutions were computed, and the mean of all solutions was calculated as the reference position. Each solution was then transformed into the East-North-Up (ENU) coordinate system to quantify deviations. To ensure data accuracy, data points with deviations exceeding twice the standard deviation from the mean were removed. The positioning solutions were folded into 24-hour cycles to analyze significant deviations during specific periods. The experimental results revealed significant deviations at certain time points, and the magnitude of deviations exhibited temporal variations. Additionally, we compute the Dilution of Precision (DOP) for each time point and visually represent satellite distribution using skyplots. These indices were used to evaluate the integrated impact of satellite distribution and solar activity on positioning accuracy. The experimental results showed that poor DOP values indicated periods of bad satellite geometry. These periods partially overlapped with significant positioning errors, which indicated that satellite distribution plays an explanatory role in positioning inaccuracies. The F10.7 solar index and Disturbance Storm Time (Dst) index analysis revealed that some significant positioning errors coincided with abnormal solar activity levels. This suggests that increased solar activity may cause ionospheric disturbances and degrade positioning accuracy, but solar activity alone cannot fully explain all observed deviations. Finally, the study examined the impact of error parameters in the pseudorange error model on positioning accuracy. The experimental results showed that satellite clock offset had the most significant impact on positioning accuracy.
Appears in Collections:	[Graduate Institute of Mathematics] Electronic Thesis & Dissertation

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