即時精密單點定位(Real-time Precise Point Positioning, RT-PPP)是一種具備不依賴地面參考站即可取得高精度成果的GNSS定位技術，其利用即時狀態空間表示(State Space Representation, SSR)格式之軌道、時鐘等改正產品消除定位誤差，使定位精度達到公寸至公分等級。然而，RT-PPP 的實務應用價值高度取決於定位收斂速度與精度能否快速達到可接受水準。尤其在電離層變化劇烈的地區，如位於低緯度電離層異常區的台灣，電離層延遲難以準確估算，經常導致定位收斂時間延長與定位精度下降。為改善上述問題，本研究採用內政部國土測繪中心透過Trimble Pivot軟體，根據台灣衛星基準站觀測資料即時產製之區域電離層模型(Regional Ionosphere Model, RIM)，透過空間內插取得待測站之垂直總電子含量(VTEC)再將其轉換為先驗電離層延遲資訊，並作為無差分PPP模型中電離層延遲項的約制條件，以降低電離層估計之不確定性，進而改善RT-PPP之效能。本研究以靜態資料模擬動態方式進行RT-PPP實驗，選用台灣本島三個GNSS連續觀測站2025年5月五天之GPS與GLONASS雙頻衛星觀測資料，並利用BKG分析中心提供之即時軌道、時鐘及電碼硬體延遲改正產品，搭配卡曼濾波器進行定位解算。透過比較引入與未引入RIM之RT-PPP解算成果，分析其定位精度與收斂速度之改善程度。實驗結果顯示，在引入RIM輔助後，RT-PPP之整體定位效能有所提升。在定位精度方面，水平方向整體定位誤差由0.13公尺降至0.09公尺，改善率達29.2%；垂直方向整體定位誤差由0.16公尺降至0.12公尺，改善率約為22.1%。其中在定位初始時刻，水平方向定位精度提升幅度達70.7%，顯示RIM能有效修正初始電離層誤差。在收斂速度方面以40、30及20公分作為定位收斂門檻值，引入RIM約制後，水平方向收斂時間分別縮短了34%、38%及29%，垂直方向則縮短了22%、19%及20%。本研究驗證了RIM能有效減緩台灣地區電離層擾動對RT-PPP之影響，提升定位效能，具備實務應用價值。

Real-time Precise Point Positioning (RT-PPP) is a high-accuracy GNSS technique that does not require ground reference stations and uses State Space Representation (SSR) corrections to mitigate major error sources. However, in low-latitude regions with strong ionospheric variability—such as Taiwan within the equatorial ionization anomaly—the difficulty of accurately estimating ionospheric delay often leads to longer convergence times and reduced positioning accuracy. To improve RT-PPP performance, this study incorporates the Regional Ionosphere Model (RIM) generated in real time by Taiwan’s National Land Surveying and Mapping Center using Trimble Pivot software. VTEC values obtained through spatial interpolation are converted into a priori ionospheric delay constraints and applied in an undifferenced PPP model to reduce ionospheric estimation uncertainty. A simulated real-time experiment was conducted using five days of dual-frequency GPS and GLONASS data from three GNSS stations in Taiwan in May 2025, together with BKG real-time orbit, clock, and code bias corrections. RT-PPP solutions with and without RIM constraints were compared using a Kalman filter. Results indicate that integrating RIM significantly enhances RT-PPP performance. The horizontal and vertical RMS errors are reduced from 0.13 m to 0.09 m (29.2%) and from 0.16 m to 0.12 m (22.1%), respectively, with initial horizontal accuracy improving by up to 70.7%. In addition, the convergence time is substantially shortened in both horizontal and vertical directions. These results confirm that RIM effectively mitigates ionospheric disturbances in Taiwan and enhances both the accuracy and convergence of RT-PPP, demonstrating clear practical value for real-time applications.

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