全球定位系統（Global Positioning System, GPS）雙頻觀測資料經過處理後，其精密單點定位（Precise Point Positioning, PPP）之精度可達公分等級。然而，對於精度要求較高之應用，如控制測量、地殼變形監測等，公分級精度尚嫌不足。欲進一步提昇PPP之精度，必須考慮電離層二、三階等高階項誤差之改正。本文在於研究電離層高階項誤差對於台灣地區PPP之影響，因此，主要研究議題為探討在：（1）不同方向（2）太陽黑子高、低峰期（3）不同季節（4）不同地區等情況，改正電離層高階項誤差後對PPP精度之影響。 實驗使用之主要軟體與服務有：（1）RINEX_HO程式，（2）gLAB程式，及（3）AUPOS服務。實驗資料，包含5個台灣衛星追蹤站2009年至2015年之GPS觀測資料。根據實驗結果發現，若改正電離層高階項誤差，對於PPP之影響有以下幾點特性：（1）對東西方向的定位精度提昇比例最高，約為63.0%。（2）太陽黑子低峰期之改正效果較佳，定位精度提昇比例為43.0%。（3）夏季、秋季的定位精度提昇比例優於春季及冬季。（4）南部的墾丁站，其精度提昇效果最佳，定位精度提昇比例約為47.3%。

The precise point positioning (PPP) accuracy can reach cm level using Global Positioning System (GPS) dual-frequency data. However, cm level accuracy is insufficient for high accuracy applications, such as control surveying, deformation monitoring, etc. To improve the accuracy of PPP, must consider the higher order ionospheric refraction effects. The purpose of this research is to investigate the effects on PPP accuracies in Taiwan region caused by higher order ionospheric refraction errors in different situations: (1) errors in different directions, (2) using observation data in low or higher solar activity period, (3) using observation data of different seasons, and (4) using observation data of different areas. There were two programs and one service applied in this study: RINEX_HO, gLAB and AUPOS. Test data sets are the observation data from five satellite tracking stations of Taiwan region of year 2009 to 2015. According to the test results, there are several characteristics after correcting higher order ionospheric delays. (1) Most significant effects on the receiver positions occurred in the east-west direction. About 63.0% of PPP results were improved. (2) Accuracies of corrected PPP results improved 43% when the solar activity was low. (3) Summer and autumn observation data had better outcome. (4) The southern station, e.g. KDNM, can get better PPP results. About 47.3% of PPP results were improved.