摘 要
本研究聯合GPS資料、水準資料、重力資料與全球大地位模式EGM96，並考慮剩餘地形理論，以點質量法平差模式計算台灣本島之區域大地起伏。觀測量包含1719個一等水準點上的GPS橢球高與水準高量測資料，以及 自由空間重力異常資料。因為點質量法和區域性質量點分佈有相當密切的關係，全球性的點質量法未必適合台灣地區，因此本文進行網格大小、質量點深度與取樣範圍等相關因素之實驗分析。實驗結果顯示，以點質量法為平差模式計算得之大地起伏在整體精度上可達9.1公分，但山區部分較差，精度約為13.1公分。

Abstract
In this study, a combination of GPS, leveling, local gravity data and the global gravity model EGM96 with the point mass model is presented for the local geoid determination in Taiwan’s area. The observations include 1719 ellipsoidal height data from GPS measurement and leveling height data at benchmanks of first order in Taiwan as well as a set of free-air gravity anomaly data. Since the point mass model has a close relation with the local mass distribution, the global parameters used in the point mass model may be not suitable for local use. Hence, the parameters in the point mass model, namely the size of grids, the depth of mass points and sampling range are investigated in detail. Our experiments show that the entire accuracy at a 9 cm level is achievable, and the accuracy in the mountain’s area is about 13 cm.

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