精密單點定位 (Precise Point Positioning, PPP) 吸引研究者興趣的原因在於不需要二個或以上之觀測站即可在全球範圍內進行靜態或動態定位。進行單頻精密單點定位面臨的挑戰與困難在於相位模稜之搜尋。在雙頻二次差分相對定位裡，可利用無電離層線性組合及差分技術消除誤差；而精密單點定位技術不同於多參考站，無法利用差分技術消除大部分的誤差，必須改正大部分誤差來源，如衛星軌道誤差、接收儀時錶誤差、對流層影響所造成之延遲量及電離層延遲量等。 本研究利用台灣自主電離層數值模型(TaiWan Ionospheric Model, TWIM)所演算出之總電子含量與Klobuchar模型來改正電離層之延遲量。並使用本實驗室所開發之ManGo單頻精密單點定位程式進行解算，成果將呈現單頻觀測量改正電離層延遲量後之定位誤差。 The precise point positioning (PPP) technique is attractive to researchers because it does not require two or more operating GPS receivers. Single frequency measurements make the solution more challenging due to the ambiguity resolution. While dual-frequency carrier phase measurements can construct an ionosphere-free linear combination to removes first-order ionospheric errors. Precise point positioning technology is different from multiple reference stations. It can not use differential techniques to eliminate error sources, such as satellite orbit errors, receiver’s clock errors, the tropospheric delay, the ionospheric delay and so on. We employ measurements of the FORMOSAT-3/constellation observing system for meteorology ionosphere and climate (COSMIC) GPS radio occultation (RO) to construct the Taiwan ionospheric model (TWIM). Compensated for the total electron content is also performed. We employ the TWIM and Klobuchar model to correct ionospheric delay. We developed the ManGo program to process the single-frequency precise point positioning and results will show the positioning errors of single-frequency PPP.
