台灣區域性電離層模型之估計：應用於單頻精密單點定位

Estimation of Taiwan Regional Ionospheric Model ：Application to Single Frequency Precise Point Positioning

全球定位系統（Global Positioning System, GPS）是一項高精度的定位技術。目前單頻定位誤差最大來源是電離層影響。本研究利用國土測繪中心提供的本島2006年e-GPS資料，使用球諧函數的概念，估計出適合於台灣的區域性電離層模型，並與IGS電離層模型作比較，分析兩者對單頻精密單點定位精度的影響。首先比較台灣上空（120E, 22.5N）之全電子含量差異，發現IGS與台灣區域性電離層模型兩者差值於各時段之RMS值為3～8TECU。進行單頻精密單點定位測試於不同時段時，使用台灣區域性電離層模型時，其定位精度可較使用IGS模型提升約80～90%。若選用一整天觀測資料，使用IGS模型時，其定位誤差RMS值為公尺等級，而使用台灣電離層模型時，平面定位誤差約為5cm，高程則約為15cm。因此得知，使用台灣區域性電離層模型可較使用IGS模型能更有效的改善定位誤差。 Global Positioning System (GPS) has been known as a high-precision positioning technology.The ionospheric delay is currently the primary error of GPS single frequency positioning. This studyfocus on the estimation of a Taiwan ionospheric model in terms of spherical harmonic coefficientsderived from 2006 e-GPS data provided by National Land Surveying and Mapping Center. Acomparison of total electron content difference between the IGS model and the Taiwan local ionospheric model at a location (longitude: 120E, Latitude:22.5N) shows the RMS is 3～8 TECU.Different ionospheric models used for single frequency Precise Point Positioning were tested atdifferent time intervals. Using the Taiwan ionospheric model can improve the positioning accuracyby 80～90% compared with using the IGS model. Additionally, if a whole day GPS data are adoptedin the test, positioning error is at meter level by applying the IGS model, while positioning error canreach 5 cm in horizontal and 15 cm in vertical after the Taiwan ionospheric model is corrected. Inconclusion, using the Taiwan ionospheric model is better than using the IGS model.

Global Positioning System (GPS) has been known as a high-precision positioning technology.The ionospheric delay is currently the primary error of GPS single frequency positioning. This studyfocus on the estimation of a Taiwan ionospheric model in terms of spherical harmonic coefficientsderived from 2006 e-GPS data provided by National Land Surveying and Mapping Center. Acomparison of total electron content difference between the IGS model and the Taiwan local ionospheric model at a location (longitude: 120E, Latitude:22.5N) shows the RMS is 3～8 TECU.Different ionospheric models used for single frequency Precise Point Positioning were tested atdifferent time intervals. Using the Taiwan ionospheric model can improve the positioning accuracyby 80～90% compared with using the IGS model. Additionally, if a whole day GPS data are adoptedin the test, positioning error is at meter level by applying the IGS model, while positioning error canreach 5 cm in horizontal and 15 cm in vertical after the Taiwan ionospheric model is corrected. Inconclusion, using the Taiwan ionospheric model is better than using the IGS model.